The system in my sig is pretty close to yours as far as cpu power and motherboard performance goes (AN35 wooo!).
My friend got a 3000+ with a DFI NF4 board and an X700Pro (fairly comparable if not a bit slower than a 9800Pro/XT).
At stock speed he gets 15,000 3dmarks (2001) and 6450 3dmarks(2003) while with all my stuff at the speed you see in my sig I get 16550 (2001) and 6443 (2003).
Basically, without overclocking his system one bit, it is pretty much at the same level as mine. With some overclocking (and these chips have a LOT of overhead) performance should far surpass mine.
Now you are in a bit of a different situation because it seems you have gotten a 754 cpu and motherboard, and the 754s probably aren't at the same overclocking/performance level, although after overclocking it is probably a bit faster than your current shuttle setup.
If you already have the combo then go ahead and install it. If you don't I would save up a little more and get a Venice 3000+ and a nice Nforce4 board.