Here's my current rig
Win 7 64-bit
920 D0 2.8ghz
1TB caviar black
My 1GB vapor-x 4870 just crapped out. I run dual monitors as I do some photo editting and a little CAD work. I frequently play BC2 and SC2 on a 1920x1080 monitor.
My main concern was that my PG&E bill spiked up around $25/mon since I've had my rig since I keep it running at least 8-14 hours daily.
Since my power hungry 4870 expired, I was considering the 5770 but I would be lacking in performance. Or should i go with the 6850. The 6950's pricing is pretty steep imo, unless if someone can convince me that it is far superior than the 6850.
I'm looking for mainly low idling power
Ultra [no AA] performance (somewhat flexible)
I would like to spend less than $200 but my budget permits $450 [SSD soon =)]
you should only upgrade your card to a new one if the new one is at least 2 tiers higher.The 4870 is faster than the 5770 actually and once it is highly overclocked the difference between it and the 6850 will be hardly noticeable so to see a noticeable difference in all games you should at least get a 6870.In case you are considering nvidia nothing less than a gtx 560 ti
I would say to invest a little more and buy a 6950 2Gb model. You will have the option of unlocking a big chunk of the 6970 potential after some time if you feel that you do not have enough graphic power. The 1Gb model can not be unlocked. It is easy to do it, it's a bios flash and almost all of the 6950 can be flashed. This also voids your warranty but i would prefer to have the option.
Keep the SSD option for a little later.
And buy a card that has good cooling.
The 5770 is not an upgrade since it has the same performance as the 4870.
As another option from nvidia a gtx570 or 560ti would be the way to go. SC2 favors nvidia cards.
EDIT: now days the cards consume less power at idle, nvidia consumes more at load, at idle they're almost the same.
If you can stretch your budget to 250-270$, I'd recommend a HD 6950 2GB.It will be a good upgrade from your HD 4870 and will last quite long as well.You can also unlock it if you feel that you need more power in the future.Otherwise, the HD 5850 is a good, cheaper alternative.
@itsgrandpa, 68xx series were meant to replace 57xx not 58xx, also they have improved CF scaling and tesselation. Probably you can find 6950 2GB for around 230-240$ also, not only 250+. Also usually nVidia cards run better than AMD on Blizzard games, but SC2 is an exception. HD 6870 runs head to head with GTX 560Ti and 6950 is not far from 570. My vote goes for 6950 2GB, OP said he uses 2 monitors, and that's the place where 2GB will be useful. Also GTX 560Ti would also be great choice, but it's a bit out of your price range. CUDA might be useful for you.