By norm if you are lagging in-game while streaming it means that your bitrate is too high but since your internet is more than qualified to stream it's either a problem related with hardware or your OBS settings. From your post I can see a few things that you might wanna look into:

Currently my bitrate/buffer is @ 3,000.
Unless you are a Twitch partner (quality options) this shouldn't be higher than 2k since most people will experience video stuttering.

Quality is at 10.
Enable CBR (tick the box above the quality drop-down menu) and CBR padding to meet Twitch's minimum broadcasting requirements.

Other than that I can't see any other "wrong settings" that would cause your problems.

That PC shouldn't be lagging as much as it is, maybe update your drivers or make sure your not running anything heavy while you are gaming.

And yes, lowering the resolution will result in a fps boost.

Yup, thanks :D

I can stream every round of the EU cup if there are casters up to the job.

Awww, sadly I can't make it because of timezones, good luck anyway.

What time is this supposed to start? I wouldn't mind streaming it if you get casters.

Also, I would suggest something like http://challonge.com/ for the brackets.

I've been using Win8 for both streaming and playing TF2, 0 problems so far.

The only thing I would recommend you doing is getting something like StartIsBack or Classic Shell since Metro UI is really shitty.

I only use viewmodels on melees

four you are the man, I've been using your HUD and cfg editor and they are amazing!

From what I can tell from the image this tool allows you to switch HUDs? If not please add this since I switch from my casting HUD to my normal HUD quite a few times and it gets annoying having to unzip (hehehe) everytime.

Other than that, the program looks great! :D

I have no idea how it works in normal play, it's made for spectating.
http://www33.zippyshare.com/v/94283221/file.html

My casting HUD (Custom BXHUD w/ OMP's targed ids)

http://i.imgur.com/hEe0M0p.jpg

With the overlay. (Wrong teams because I'm lazy...)

http://i.imgur.com/YpY2JLS.jpg

I would love to help you guys out, I meet all the requirements and I've been running my own TF2 casting/streaming channel for a while.

I'm a super nerd so availability is not a problem.

This won't work on live STVs since player views are only binded to slot1-12 when you enter as a spectator in the actual server the game is being played on.

http://www.twitch.tv/duckypt

For the majority of the time, I will be casting TF2. I might also stream some mixes, wars and some DM or MGE action. I can also stream at 720p 60fps with a webcam if I'm felling pretty.

I currently live in Portugal.