I'd go with a third party access point or router (the Netgear line is getting lots of good press here, but they aren't the only brand to choose from) and an AirPort Extreme card.
Reasons: Apple is just too proud, pricewise, of the AirPort Extreme base stations for what you get, with the least expensive model costing about $200 the last time I looked. In comparison, you can get a different brand of 802.11g wireless router (not just an access point with a single ethernet LAN port) for about half of that, and less if you shop for sales.
The best reason to go with an AirPort Extreme card is the tight integration of the AirPort software with OS X. These cards aren't terribly expensive, they're guaranteed to work with your Mac. If your computers don't both support the Extreme card (the Extreme card is a different form-factor from the original, PCMCIA-like AirPort card), you can go with an orignal card and just live with somewhat slower speeds-which you won't notice in normal surfing.