There are too many variables, and your question isn't properly defined.
Which is faster, is the Core 2 Duo, the video card won't make a bit of difference in that. You need to add some sort of condition to gaming or rendering if the GPU is factoring inot it, then you should also note the app you are using as some will utilize the 2 cores and some it won't make a bit of differnce to.
A Turion isn't Sli just because it is a Turion, the system would need to be Sli. So if we are talking baout 1 video card vs. another, the 7900 GS is probably a faster/better card.
A Core 2 Duo would wipe the floor with a Turion CPU vs. CPU, that you are right.
You may want to go to my page and check out the Mobile GPU comparison page and the COre Duo & Turion page, it is in the menu under SPECIFICATIONS
That;'s about $500 more then my budget for a laptop
The thing is, while I have 4 high powered pcs, and a total of 17 pcs (I even have a tandy 1000 and a couple commodore 64s!), I'm not super huge on laptops. maybe I'll get that way, but the budget isn't going over $2000 for now.
Also, I think the Area 51 m5750 is beginning to grow on me. Built to last, x1800, core 2 duo, long battery life for a desktop replacement, cool, seems to be exactly what I'd want for my first laptop...
Bottom line with KillerNotebooks is that Mark uses all quality parts and he's easy to deal with. I've had my Wakizaki for a week and I'm very happy with it. It won't hurt to PM him the least you'll get out of it is an idea of whats out there.