You can also use Tom's hardware for comparison, although again it is desktop, and not on the same page (same games and tests though). Notebook scores tend to be about 10% less than equivalent desktop versions.
Tom's hardware tested in many popular games, so after clicking links below, check out other games tests as well.
PCIe comparisons Far Cry test using AMD A64 4000+ (top of the line system).
1024x768x32 default (no AA or AF) X300 scores 17.6fpshttp://graphics.tomshardware.com/gra...charts-07.html
AGP comparison in same Far Cry test using Pentium 4 3.2 GHz (mid range, more like laptop)
1024x768x32 default (no AA or AF) 9600 Pro scores 22.4fps.http://graphics.tomshardware.com/gra...charts-08.html
Considering the 9600 pro is in a P4 system that may be 75% as fast as the AMD system that the x300 used, yet still the 9600 pro is 30% faster than the x300, I would guess that the 9600 pro is about twice as fast as the x300, if used in identical systems.
You would be very disappointed going from 9600 Pro down to x300.
X600 is better, but still no upgrade, as it scores 21.6 in same test, even though it is in a much more powerful machine. Looks like X600 would be about 80% as fast as the 9600 pro in same machines.
I "mild" upgrade to the 9600 Pro would be going to the ATi X700 or nVidia 6600. Anything less would be just less.
BTW, using the above benchmarks as a guide, guessing that the x300 would only score around 11fps if used in a system like the P4 3.2 GHz, even less in Pentium M 1.8GHz notebook, and it is of course totally unplayable. Even if you lowered the resolution, you would have a tough time gaming. On the other hand, the 9600 Pro is almost playable, with simply lowering resolution slightly the only thing needed. X300 is NOT a gaming card.