I'm running a D-Link (looks for box) DI-624 basestation for my Powerbook. Based on what I have seen, I am getting 5 times the speed I got on 802.11b; about 20-25mbps practical speed.

Should be enough to stream the needed 600k/s per stream from your ReplayTV to DVArchive.

Do be careful of 802.11b equipment though. It can drop the entire g network back to b speeds. I set my g router to only allow g clients to avoid this.