#1004
I'd go with Skylake, CPU prices should be pretty much the same now, DDR4 would be around the same price at the same speed (although you'd go with 2400 instead 1600MHz so slightly more expensive) and the new chipset features are worth the slight premium on the mobos imho. Bonus: LGA1151 will be around for a while, Kaby Lake in 2016 and Cannonlake in 2017 will still be using it, so only if you upgrade after summer 2018 you'd need a new mobo.
CPUs don't change that much so a more normal upgrade cycle instead of 1.5 years would be around 5-6 years for CPU + mobo + RAM (maybe complete build) and replacing the GPU 2 or 3 times (so every 2-3 years) during that.
pcpartpicker doesn't know a lot of shops outside of US/CA/AUS so this is far more expensive than it needs to be.
CPU and therefore mobo and RAM replaced, some parts swapped for equivalent and/or cheaper and/or better parts.
CPU: i5-6500. Performance should be about the same, but Skylake which got DDR4 support (Haswell doesn't) and is on LGA1151. which got chipset with some more features than LGA1150 did.
Mobo: GA-B150M-D3H. The main point of a mobo is that it connects everything. ATX vs µATX pretty much only means more PCIe/PCI slots, not really a concern if you're not going to use multiple GPUs or lots of other cards. You get e.g. SATA Express and M.2 and DDR4. I'm not sure if you understood that correctly because of the way you worded it. The i5-4590 (or Haswell in general) doesn't support DDR4, so you wouldn't have been able to upgrade. DDR4 isn't much more expensive than DDR3 so upgrading (=buying twice) would be more expensive anyway. Either way though mobos only support DDR3 or DDR4, not both (there are some exceptions but you'd pay extra for that). Replacing mobo and RAM just to get DDR4 definitely isn't worth it. It's still within budget so I went with DDR4.
RAM: See mobo. 2x 4GB 2400MHz CL15 or better, standard stuff. Brands don't matter, only specs and price do. This isn't server stuff with FB/R/LR DIMMs where you have to pay attention to compatibility lists. Even mix and match would work. This is tied to the mobo as well, but 2 DIMMs for Dual Channel and a mobo with 4 slots so you could in theory still upgrade if you ever need to just by adding 2 more with the same (or at least similar) specs instead of having to replace them with 2 of twice the capacity.
HDD: Not sure where you read that about reliability. Most HDDs with similar age and specs will perform pretty much the same since all 3 manufacturers that are left (Seagate, Western Digital, Toshiba) use very similar sometimes even the same technology. E.g. WD bought Hitachi, now HGST, another part of Hitachi went to Toshiba and all of them including Seagate buy some of their stuff, platters, sometimes even tech like read/write heads from SDK and TDK.
Back to reliability. Average life expectancy for an HDD is said to be 5-6 years. All HDDs will fail eventually and you should expect them to do so. An average of 6 years doesn't mean all HDDs will live that long. Some will fail almost immediately, some after 1 years, some last 3 and so on. There's nothing you can do about that. What you should do instead is backing up anything that you can't afford to lose. That reduces the impact of an HDD failure from "catastrophic" to merely "annoying".
The Seagate Barracuda 7200.14 (ST1000DM003) is usually cheaper than the WD Blue and performs as well or better. But you might not need it, keep reading.
SSD: The surprise guest. You can afford it (trust me, you'll see). The far lower boot / program start times are worth it.
The Samsung 850 Evo 250GB is the default recommendation. If you don't need more than 250GB for now you could ditch the HDD alltogether. You can always add an HDD (or multiple) later. Getting an SSD later and having to reinstall Windows is a pain in the ass.
GPU: Yep, 380 is where it's at. 1080p Ultra 60fps in FO4 isn't exactly limited and the price is great. Asus Strix, "bonus": it uses 1 8pin instead of 2 6pin connectors, you'll see why that's a bonus soon.
Case: N200. It doesn't have a lot of room for cable management behind the mobo tray but it's hard to find anything better at that price, which is why it's still my default budget recommendation.
PSU: There's two things I don't agree with here. First of all it's a 360W build. Even a Fury X would only push it to 450W. So scale down on the wattage a bit and save some money. Secondly the N200 does have a lot of space in front of the PSU. Now think about which cables you could even take off. Mobo and PCIe power connectors will all be in use. You'll need one for the HDD and/or SSD. That leaves one or two SATA power cables that you could remove. Is it worth paying 20€ for that? Not really.
About brands: Again brands don't matter, but for a different reason. Be quiet doesn't build any PSUs. HEC, FSP and Seasonic do that for them. Yes, there's the customer support, but I'd rather get a good PSU and never have to deal with CS instead of having great CS that replaces the PSU 3 times no questions asked because it keeps dying. One thing to keep in mind is that while the manufacturer is important for what they can do in terms of the uppoer limit of performance, quality and quality control they'll only do what they are paid for. So if a "brand" tries to increase their profit margin bad things can happen. An example would be the Corsair RM series, two full recalls on the Chicony models because they kept overheating (3rd revision built by CWT) and lackluster QC on the CWT models on top of mediocre performance and overinflated price. Compare that with the RMi (slightly overpriced) and RMx, both built by CWT and pretty darn good.
Back on topic there's some better, far cheaper although non-modular Seasonic models. It was Seasonic by the way who built the top of the line models that earned be quiet their reputation, whereas the L8 CM line is built by FSP and HEC. Skylake and DDR4 mean even lower power consumption and since the 380 Strix only needs one 1 8pin PCIe power connector you can get away with a Seasonic S12II-350. The downside is that you can't really upgrade to any GPUs above 200W. Those wouldn't really be midrange/sweetspot anymore so I doubt you'll do that. If you'd still like the option there's the S12II-430, but it is more expensive.
Here's the list:
CPU: i5-6500 203,49€
Mobo: GA-B150M-D3H 80,12€
RAM: 8GB 2400MHz CL15 46,12€
HDD: Seagate Barracuda 1TB 44,84€
SSD: Samsung 850 Evo 250GB 77,06€
GPU: Asus Strix R9 380 189,08€
Case: N200 44,41€
PSU: Seasonic S12II-350 36,45€ or
Seasonic S12II-430 50,83€
Total: 721,57€ (350W) or
735,95€ (430W)
Used mindfactory prices.