Archival, I think I have a Hawking + Apple adapter in a box somewhere. If you wanna work something out for it, let me know.
I have two Time Capsules and use the WDS software built into extend range, but still share same ports, etc. Works like a champ. Remember that your new Mac is 802.11n, and the Airport you have is 802.11g, so you are already stepping down a notch. I'd suggest grabbing a couple of Airports and getting on with it. Price being a factor, I know you are exploring other options. Again, let me know if you want me to dig for the Hawking.
keytohwy