^ i doubt you need an rx480 if you're only updating now because of your monitor
also the 750ti isn't a much better graphics card but its like $100, very slim power requirements and has a dual link dvi-i and a dual link dvi-d. basically just go for the cheapest one of these you can find i guess (except zotac/palik, they're less reputable brands)
just saw your post about no power supply cables, you CAN get 750tis that can draw power only from the mb though they're harder to find, personally id spend most of the extra money on a new power supply (especially if your current one is old and from a less reliable brand)