Select a graphic Card that could easily work with Adobe Mercury Playback Engine( MPE ).
Here is a list for GPUs that work well with MPE:http://www.adobe.com/products/premiere/performance.html
It is very very useful if you do more with Adobe Premiere. A for example ZOTAC Geforce gtx 570 you can afford for about $320 today but rendering is very faster for your video editing needs. [ GTX 470 also works well about ~120 less than 570 ]
And to be honest
you absolutely need at least a SSD drive for Windows/Programs partition.