Build a system using the Antec Aria case... It supports any/all micro-ATX mobo's out there, which have 3 PCI slots, plus one AGP slot. I built one not that long ago, using the Aria case and it's really quiet. I since gave that system, redone since it was running as a server, to my cousin. From <6' away I could barely hear the fans in the system (PSU fan, additional case fan provided by Antec, and processor fan). When sitting about 8' away from the system you can't hear it. You can get an MSI mATX mobo for the Athlon64 that will fit within the case. Plus, you can install up to three hard drives into the case, plus one optical drive (no floppy bay).
Personally, I ONLY have laptops with wifi. ALL my desktop systems are networked via Cat5e cables. With so many [quality] logic boards shipping with Gb networking you can't even get close to the same speeds with wireless.