Personally, I've always found those consumer-oriented firewall/router appliances to be too arbitrarily limiting. For example, a friend of mine has one, and there's a maximum of about a dozen port forwards you can configure, and they're fairly limited themselves (though I can't provide specifics right now). But, then, you already know that, since you already have one.
Given what you already have, I think your best bet is to just buy an 802.11 <-> Ethernet bridge (read Access Point). They're not all that expensive these days, and you won't be tied in to a specific router. That is, if you wanted to switch out your current Linksys router for something else, whether it be an OpenBSD ipf machine or your Mac or whatever. Plus, it should cost you less, probably even if you were to sell your old router on eBay.
Edit: Then again, I could be wrong about the pricing. Especially considering I just looked and I am.
It looks like the difference between an access point and an access point/router is about $20. I'd still go the multiple device way for configurability's sake, but I was wrong about the pricing.