So, since by yesterday Comcast had not fixed my routing problem between my two computers, and my DSL investigation showed I could only get a low speed IDSL, I went ahead and replaced my old Apple Graphite Basestation with a new Airport Extreme Basestation, which also allows wired machines to attach.
Got it set up pretty quickly. Set up ares with a fixed internal IP and put it as the "default host" on the base station so external traffic would go straight there. Set up a new dyndns host entry for the internal address of my laptop. All was working great, I can do everything I used to be able to at my old apartment.
But... I've been having problems with the whole damn thing going down periodically, losing connection on both computers (wired and wireless) until I reboot the basestation. Sometimes this was happening as frequently as once every ten minutes. That is of course unacceptible.
I've been playing with adjusting settings and things to try to stop it. I've been online almost an hour this time without getting shut out. Crossing my fingers.
But... searching online I've seen that this problem is known by a bunch of people. It was fixed for most people by a firmware update a month or so ago (which I already have). But for others, it seems like they had to return the base station and get a new one, at which point it worked.
I'll see what happens. I hope I don't have to return it. I hate returning things.
But I should be able to cancel the second IP address if this starts to work and save a couple bucks.