I just built the exact same system for my friend about 2 weeks ago. I love Antec cases and their reputation as a power supply manufacturer is very good. We went for the Antec Sonata case and used stock cooling on the retail Athlon64 3200+ CPU. Let me tell you that system was so friggin quiet that you could barely tell that the machine was on.
Unless you're planning on overclocking (always risky...and do you really notice the difference outside of benchmarks?), you can stick with the stock AMD heatsink and fan...I left the thermal pad on there too...you might get a degree or so difference if you went with some kind of Artic Silver (probably use the Ceramique since it is less messy than the normal stuff)...again you're fine with just the thermal pad on there though...just remove any plastic protective film that might be on it before installing.
Just some things to know about the rig:
1. Try a USB 2.0 memory stick or device in the front USB ports. If WinXP tells you something like "you're using a hi-speed device in a low-speed port" then you should contact Antec's tech support for a USB port replacement. Apparently they got a bad batch of them at some point...not restricted to this model case either. Of course my friend's case had the correct one in it already, so this may be a non-issue.
2. The front LED lights up blue. It's the the two side half-circle bulbs on the sides of the front USB & firewire port. Depends on how anal you are with the way the case looks... http://www.newegg.com/app/viewProductDesc.asp?description=11-129-127&DEPA=1
3. Also the purple drive rails are for the 5.25" slots are on the back of the bezels. My friend had already mounted the motherboard into the case so I didn't have it layed down to notice where they were hidden. You can see it on NewEgg's picture #5.
4. It's a 380w power supply but that should be plenty for a few hard drives, CD/DVD's, etc.
5. Don't forget that the VIA K8T800Pro chipset has AGP & PCI and not the newer PCI-express (PCI-e).