The Hardware forums could help likely the best. No offense but you'll get some uneducated/bad recommendations here (but not all are bad!) since most Hardware forum posters don't frequent this forum to help.
If you're willing to build then it can be worked out around your budget for the best bang/buck. If you don't want to build and want ready-made, contact TilDeath he's really the only person I'd trust not to completely rip people off with 300$ build charges like Dell.
If you want to run AH maxed you're looking at anywhere from 700-1500$ (I run maxed for 850$). Also, if it can run AH maxed, you don't have to worry about everyday needs as it will be good enough to do anything simpler with ease.
Mostly you'll want to look for a few brand names: Gigabyte, ASUS, SeaSonic, Corsair, OCZ, EVGA (not real sure on reliable ATI brands, Western Digital, Intel (or AMD if budget is tight), and some others but those are the biggest. Case/DVD-drive/Sound-card/other peripherals are basically personal choice since it depends on what your setup is and what you need done.
Also, if you want, if you find something you're considering buying post a link here and you should get feedback on if it's reliable/worth it.