I'm in a similar situation. I fried my ancient SMC wireless router on the weekend so now I'm looking for options - preferably cheap but still usable. Any suggestions would be appreciated, and I'll post here if I find good options.
I also have an old Sawtooth that I use as a server of sorts. I surf on my TiBook but use the big drives in my desktop to hold music, video, etc. Using iTunes music sharing works fine (I plug my TiBook into the home stereo and stream the music). The only annoyance is that play counts aren't updated when you stream (very minor) and you can't use features like Party Shuffle (much more annoying). Video streaming over Airport does not work for me, but that's likely because TiBook wireless is terrible compared to modern laptops. Streaming over ethernet works fantastic.
Any file synchronization I do is manual. There are third party apps that profess to keep folders in sync, but I haven't taken the time to give them a try. However, I know that OSX 10.4 is supposed to have a lot of new iSync features, including the ability to share Mail folders across computers. It sounds very promising.
Good luck, and I'd be curious to hear how it turns out for you.