PC Upgrades - One last component

[Mike2007x86]

I am looking to build a good quality gaming pc that goes well with a 22" Samsung 226BW monitor. Since my gaming resolution is 1680x1050 in almost any game. I shouldn't need that much graphics power to achieve stable gameplay at a such a
low gaming res.

I need help choosing a video card that can run all of the newest games at this resolution with all details maxed out. Would you suggest a 280GTX, 9800GTX, 9800GX2, 1 Additional 8800GTX, or 2 Additional 8800GTX.

I am looking to save as much money as I can, but also want to be able to enjoy all my current games in full detail. On a single 8800GTX witcher has mouse lag when I enable 4x AA so this tells me that my single 8800GTX just doesn't cut it.

Witcher and Crysis are the current games I am playing so lets focus on that as a starting point since its demanding.

Also I wanted to know whats the difference in a 9800GTX vs a 8800GTX? Is the shader and rendering quality better? Does it have a newer shader model? What does the 9 series have over the 8 series I currently own from a gaming standpoint. I am trying to understand why consumers in general buy a 9800GTX if it uses the same core chip.

I remember jumping from an FX5200 to 6800 Ultra - Some difference, but not too impressive. Then I jumped from a 6800 Ultra to an 8800GTX where I first got to see shader model 3.0 in action on splinter cell chaos theory. WOW what a difference.

I have been out of the graphics card loop for awhile so I definately need help in choosing whats best without spending too much for power I won't need since 1680x1050 doesn't require too much of a graphics card.

If I went ATI instead of nvidia, how stable is there driver support now for vista 64-bit.

I currently have a 680i motherboard that I use with my Q6600:
If I upgraded my motherboard, would I see any noticable difference going to a 780i or a 790i over what I have now? I primarily use my pc for 90% gaming and 10% video encoding and of course everyday work and c++ programming.

Please help me choose whats best for the gaming resolution I normally use.

Also, is there any need for a Aegia BFG Phyx card these days?
Should I upgrade my sound card from a XFI Extreme Music to a XFI Gamer audio card or stick with what I have.

 

[Dangman]

If your motherboard is working just fine, no need to swtich to a different motherboard. You won't see any noticeable performance increase from going to the 700 series motherboards.

And no need for Phyx card or sound card upgrade.

Video card wise, read this review to see the differences between the 9800GTX and 8800GTX:
http://hardocp.com/article.html?art=MTQ4MSwsLGhlbnRodXNpYXN0