APPROXIMATE PURCHASE DATE: Probably within the week if i can get a good answer
BUDGET RANGE: $250 max
USAGE FROM MOST TO LEAST IMPORTANT: WoW, Starcraft, DC Universe
CURRENT GPU AND POWER SUPPLY: Radeon 5770, and i think 450 but am willing to upgrade if necessary ($150 max on power supply if you can give a suggestion on that too)
OTHER RELEVANT SYSTEM SPECS: Gateway FX gaming desktop, i7 processor
PREFERRED WEBSITE(S) FOR PARTS: newegg, tigerdirect, bestbuy
PARTS PREFERENCES: wat ever is the best
MONITOR RESOLUTION: 1680x1050 but might get a 1920x1080
ADDITIONAL COMMENTS: I know that wow dosnt need a demanding card but im looking for a better one anyway. I have 2 monitors running on my 5770 and dont feel like its doing th job. I play WoW/any other game on one and ususally internet on other.
Any GPU solution (single or dual) in your price range is going to require more than 450w, especially if you have your processor OC'ed. There rarely is a single answer, but usually people want the best performance for their price limit. Not sure if you favor either company so I'll list your best options from both camps:
6870- $210-$240 HD 5850- $180ish (I normally wouldn't suggest this, but they have an XFX Black Edition for $180 after MIR- very solid deal)
HD 5870- can be had for as low as $240 after MIR. Will outperform the 6870
Note: the 6850/6870 tend to scale better in crossfire than the 5850 so if you are considering that upgrade path take that into account.
Superclocked GTX 460: $180-220. The EVGA 460 FTW got great reviews but looks hard to find right now.
GTX 470: can be had for around $250
The GTX 560 should be coming out soon and will most likely fall right into this price range.
Last note: if you can stretch to $280, the HD 6950 can be had for that price after MIR right now and it can be BIOS flashed to a HD 6970. This offers performance right at the level of a GTX 570/HD6970 ($350-$370) at a $280 price point! This is a pretty incredible value right now and is the talk of the town in the enthusiast GPU world right now. I would recommend you take this route but it does fall above your stated budget.
Your first option could be to crossfire with another 5770 if your motherboard supports it and you wouldn't mind doin it, its suppose to be a great crossfire option alternatively you could go with a GTX 460 which is under $200 and a small step up from what you have then on the $200 budget you could just about afford a 5850 which is $180 after rebate ($210 before) this is probably your best option as single GPU setups are more realiable but unless you can sell your current 5770 it will also be the dearest.
Others to factor in: the 5830, bit overpriced but still a good card if found at the right price. 4890 bit old now but still a powerful card but without the dx11 it not might appeal to you.
sorry for some reason thought your budget was $200 well on top on what i said you can also afford a 5870, 6850 and 6870 all are good cards and as the previous writer said the 6 series tend to scale better but the 5870 is probably the most powerful out of the lot.
For PSUs my OCZ StealthXstream 600w is great, along with my sapphire hd6850 toxic. Those games are not too demanding, so I think a hd68xx or a gtx460 or above should be enough. You could CX your hd5770 too, might not be a bad idea if you do not want to break the bank.
If you decide to purchase a new power supply do not go cheap. Get one of the modular PS's rated at 750W or higher that way you have future growth potential. The two things you should never go cheap on are motherboards and PSU's, because low quality in either will give you headaches and frustration for months.