It will be faster then your P4 and it will be a significant gain in performance. However, this guy selling point is its low power usage. I know a lot people like it for HTPC's because they are quite and don't suck that much power.
If you are going dual core I would recommend an Intel Core2Duo.
edit: I'm going to do some research and see what type of combos I can come up with brb...
I just found out that my motherboard is not compatible. (At least I'm pretty sure.)
The socket is ok (LGA 775), but it says the FSB is only 800 or 533 mhz, and the processor you linked is 1066mhz.
The RAM compatibility is severely out-of-date on the motherboard to, "Support for DDR 400 MHz and DDR 333 MHz"
So it looks like I'll be upgrading motherboard and processor within the next few weeks *if* I am not happy with the performance of my new xfx 9800gt.
Thanks for the continued help!!!
Edited by Korrect Method - 12/16/08 at 10:09pm