Your diagram may lead others to think that my setup is more complex than it really is. If you want you can stretch the whole thing out in a straight line:
Bridge#3 <---> Main Router <---> Bridge#1 <---> Bridge#2
Bridge#1 = RTV#1
Bridge#2 = RTV#2
Bridge#3 = Desktop Computer
Main Router = DSL, DHCP server, network printer, desktop computer
So in terms of bridging my DSL internet connection, I am bridging two networks to the Main Router. In terms of ReplayTVs, RTV#2 is bridged to RTV#1, and the whole thing (Bridge#1) is bridged to the Main Router.
They are all on the same channel with the same broadcasted SSID, so yes you could walk around my house with an 802.11g enabled laptop and associate freely (roam) with whichever basestation you happen to be closest to.
BTW, on a Mac there is actually an option to "Join Network With The Strongest Signal". Can someone tell me if there is a similar feature for Windows XP??? The only thing I can do is list access points in order of preference, so even if AP#2 is twice as strong as AP#1, the PC will still connect to AP#1 since it is listed first in the Properties panel. Any help here would be greatly appreciated.
Your question about having other things hooked up to the WBR-G54's while streaming or doing other things is difficult to answer. I would only say that bandwith, even on a completely wired network, is fixed like a pipe installed underground. Throughput, or what you are trying to get through that pipe, is a different animal altogether dependent on a multitude of things. Adding wireless to the mix introduces a lot of extra variables. You'll just have to try things out with your particular situation.
And definitely let all of us here know how it works our for you!