If you've got ~$185, the All-In-Wonder X800XT
looks to be a decent card from ATI. From Newegg, I didn't really see any ATI cards that are AGP 4x that were better.
EDIT: BTW, I couldn't find a non-All-in-Wonder from Newegg, though I'm pretty sure they exist. If you want to look elsewhere for one, they may be cheaper than the All-In-Wonder version.
EDIT2: You shouldn't need another fan for your system if all you're doing is adding a video card. The video card comes with a fan on it, so unless you're just not satisfied with the cooling performance, there's no need to replace it.
And I think it has to say "4x/8x" or just "4x" in order for it to run in your AGP slot. I'm not entirely sure of this, but better safe than sorry.