My video card died (in a most peculiar way), and I am looking for a replacement. Unfortunately, I don't have on board video, nor do I have an old card I can throw in, so my components list will include some best guesses.
MSI P45 Platinum
Core 2 Duo (approximately 2.2 - 2.3 GHz I believe)
2 x 2 GB RAM, 800 MHz
big fat PSU (750 W or something like that)
Old card: 7900 GS
So here's my issue: for any good card the bottleneck will be my cpu, and it seems like a waste to upgrade the cpu without just buying an entirely new system, which is not an option. My original plan was to buy a second 7900 GS when I needed it, and keep that configuration until I got a new machine in 2 years. 2 x 7900 GS is still a bit cheaper than a 9800 GT. I game but don't need to play on high settings to enjoy it; I'm more concerned with FPS than resolution.
Will something like a 5770 / 4870 be so overpowered, and bottlenecked so severely by the cpu, that there's no noticeable performance increase over a 9800 GT (or 2 x 7900 GS)? If the 5770 has enough longevity to last me 3 years, so I won't have to replace it right away when I get a new system, it might be worth it. Should I consider the directx 11 support, or will I be alright with 9 for 2 more years (I currently run XP)?
Power consumption is also something to consider. If using a second card costs me 20 cents more per day, that's about $73 per year.
Im no expert to tell you if a 4870 or 5770 would be bottlenecked by your ~2.2GHz CPU but I do think that its a good match up. Maybe even the 4850 or 5750 if you are so concerned. My guess would be that they would give you a noticabe performance incrase over a 9800 GT even if they are botlenecked by your CPU.
Seeing as you are essentially starting over in buying a new card Id buy a single powerfull card now with the possiblility of crossfire/sli rather than buying two cards to crossfire with now.
How much bottlenecking will occur depends on what resolution you are using. At low resolutions you are going to be cpu bound and probably won't see much of a difference between a 9800gt and an HD5770. At medium to high resolutions you will definitely see a difference especially when using high settings/AA.
You should at the least OC that CPU. Core2duos overclock very well and I wouldn't be surprised if you can get it up to 3ghz fairly easily. That would make a big difference.
But, I do think you should consider upgrading that CPU. You basically have the absolute worst core2duo possible. With a P45 board you can handle any of them and an upgrade to a good core2quad will be huge.
Thanks for all the responses. I priced some Core 2 Quad, and they're about $200. So if I got a good card and upgraded my cpu, that's about $300 more than just getting a crappy card. I'd rather put that money towards an entirely new system, so I decided to get a cheap card (HD 4650, only $40!) and anticipate getting a new system in 1 year rather than 2.