My situation is this:
I bought my PC in 6/2008 pretty cheap with 2x GeForce 8600+ GT's in SLI driving a 1280x1024 display. Things were exceptional. Then I bought a new monitor operating at 1920x 1080 and want to maintain graphics quality with a single card on my primary display. Plus one of my 8600's cooling fans is dead, so I'd like to replace that one anyway. I'd love to hear some opinions on what to purchase, what not to purchase, and waiting for price drops and such. I was thinking of going with a GTX 260 for christmas time : )
2x Nvidia GeForce 8600+ GT
2 Gig DDR2 Mushkin RAM
AMD Athlon 64 X2 Dual Core Processor 5000+ @ 2.73 GHz
420W Power Supply
ASUS M2N SLI AM2 Nforce 560 mainboard
Apevia X-Telstar Jr G Type Case
OS: Windows XP Pro
ASUS 1920x 1080 23" display
AG Neovo 1280 x 1024 19" display
Yeah, a GTX 260 would be pretty good for your resolution but the HD5770 is DX11, a bit cheaper and much more power efficient/cooler while offering similar performance. The only issue is that your board is SLI so you won't be able to use 2 in crossfire at some point if you wanted to.
If you have the money you could go for an HD5850, that should be great for your resolution for a long time so not being able to crossfire won't be a big deal.
With an SLI board, you have more choices w/ nvidia .... for example, where that article points to a tie between the 4870, 260 and the 5770 at the $155 price point ..... the same three way option isn't available to you at $310.
The question then becomes, do I buy with the thought of not buying more card than is appropriate for the system or with the thought of taking this this card / PSU to another box in a future build ?
For 1920 x 1200, the entry point is the $125 range where a 4870 512 MB is listed in the article at $125 ....yeah right .... they start at $180 on newegg. So now we're back up to that $155 price point which really means $175-180 for the 260/4870/5770.
But now we have to consider PSU issues .... w/ 2 GTX 260's ... using the calculator linked below I came up with 452 watts which, with a 20% cushion, would call for a about a 550 watter.....but that would put your GFX subsytem far above the rest of the box. With just one, your old PSU should hold up if it's half way decent.
I am in the exact same boat with you with my old 8600gt SLI rig, this card I posted above is 10x better and a very reasonable price for that quick upgrade. Plus it has HDMI connector built in, which is rare on Nvidia cards except for very high end. I am running two of these in SLI on my Asus 1920x 1080 screen in 1080p and am maxing out Dragon Age Origins. Choice is yours but these cards are your best bet for a quick and cheap upgrade that you will def notice the difference in power.
A GTX260 or a 4870 1gig card would be a very good upgrade. The 5770 might have similar numbers to these 2 cards but the real life performance equivalency isn't there. I can't understand why people equate the 2. Also it would depend on your opsys. xp..? Then no need for a DX11 card. Someone brought up the power supply. If the one you have has 35-40 amps it should be fine. If less the system will suffer.