Total comes to $363 without shipping. That leaves $140 for your video card. That won't get you much. I would keep your 7800GT for a little bit longer. It'll still play every game out there, just not on Max-Ultra-Uber settings.
Don't waste your money on a new video card. You have a nice 7800GT. You'll be able to play all the big games coming out soon. Get it when you need it.
I still have a Radeon 9800Pro. I'm upgrading to a 8800GTS this month. There's a nice jump when you jump from 2, or 3, generations of hardware. But not a lot when you jump from 1.
Plus, you're gonna be in college. Focus on your studies. (that's extremely hypocritical of me. I'm building a gaming rig for "college". )
Okay, right now it's a toss up between a Core 2 Duo E6850 Conroe and a Core 2 Quad Q6600 Kentsfield. Both perform similarly according to Tom's. Which way should I go?
Because it's all marketing. The E6850 is new generation (1333Mhz FSB). The Q6600 is basically 2x E6600's in one package. The E6600 is older generation (1066Mhz FSB). When the new generation came out, Intel dropped prices on the Q6600's and if I'm not mistaken many others from the old gen Core 2's.
Whether or not the quad is a good deal for you, depends entirely upon what you plan to use your computer for. Gaming? No big upgrade in performance from Duo to Quad. Simple apps (Word, Internet, etc.)? No big difference. Video editting? Big difference. 3D rendering? Big difference.
If you plan to keep this computer for more than 2 years, it's probably worth it to go with the quad core.