I'll have to first agree with the "don't buy branded computers" persons here. I managed to buy and build my own rig that was more powerful AND CHEAPER (by about $20) than a branded computer I had for all of three weeks before it died on me.
Anyway.
Do not get a physics processing card. They're an absolute waste.
You may want to look into a larger harddrive as well.
A better video card may also be worthwhile. There are substantial leaps from the 8600 to the 8800.
Just as a point of reference, here's my own build that cost about $1100:
-Core 2 Quad Q6600 -
$289 (This is about $10 less than what I paid even)
-EVGA GeForce 8800GTS (320MB) -
$280
-MSI P6n Platinum (650i Chipset) -
$150
-WD 250GB SATAII HDD -
$65
-OCZ GameXstream 700W PSU -
$145
-Cooler Master Centurion Case -
$50
-Kingston 2x1GB DDR2 800 RAM -
$83
-Used my old (only a few months)16x Double Layer DVD burner
-Used an internal Wireless card I already owned
-Opted to not use my X-Fi ExtremeMusic card just using the built-in audio
If I were to make changes. I'd say go with some lower latency RAM than what I got, and a third-party CPU cooler instead of stock. You could also get away with a powersupply with less wattage than what I opted for, but I wanted mine for future use and upgrades.