Your current system is nicely balanced an upgrading would be a waste of money. Personally, I think it's a great computer.
Anyway, you should be building a whole new system. Based on your attitude I'm going to say build around X58
it's not hard after that. example:
1) X58 Mobo
http://www.ncix.com/products/index.php?sku=34542&vpn=GA-EX58-EXTREME&manufacture=Gigabyte
2) Core i7 920
3) 6GB DDR3 kit (3x2GB) i saw Corsair at Newegg for $82 after rebate
http://www.newegg.com/Product/Product.aspx?Item=N82E16820145236
4) graphics: (2x NVidia GTX 275 896MB)
5) case (Antec 300?)
6) Heatsink Fan combo for CPU
7) 2x 120mm case fans
8) Seagate 7200.12 500GB or the WD Black 640GB if the extra noise isn't an issue maybe 2 drives in RAID 0 (Windows drive)
9) WD Green 1TB (backup, downloads, media etc)
10) PC Power and Cooling 750W
This is expensive. As I said, I think your current system is nice.
Why don't you hold off another year and build a system which includes these specs:
- DirectX 11 Graphics card
- SATA 3.0 (600MB/sec throughput, SSD is going to kick SATA's ass soon)
- Windows 7
- 32nm CPU, possibly 6-core 4GHz
- Larrabee?
- better support of HDMI audio
Noise and Power wishes:
- we will see overall noise and power optimizations but most importantly we hopefully see something like "HybridPower" come back so the graphics card can turn off completely and use an efficient on-board graphics chip. I'd love to see that applied to the CPU as well. imagine adding a simple connection (like the new ATI XGP) that allows a CPU/GPU external brick to be plugged in?
With the new "ION" nettops coming and the low-end Mac Mini being able to idle at 13W I am expecting an increase in the drive for a PC gaming system that can idle cool and silently.
I think we'll see a huge change from now to a year from now in the gaming PC.
I do think NVidia's 3D solution will catch on eventually. It currently requires the computer to run twice as hard; the monitor must be driven to 120Hz for you to see games at 60FPS through the goggles which filter one eye each frame. However, this issue will be easily solved by a "frame doubler" chip prior to the output which would consume very little power.