You're on a budget, so you probably don't want an Airport, but just for reference I bought one of the full-on base stations (the mini Express ones are cheaper), and it was amazingly easy to set up--totally plug and play with my SBC DSL modem, although I fiddled with the security settings--and has run perfectly for the past month at least.
Contrast this with my brother's 2Wire modem/router combo (also with SBC DSL), which was a big hassle to get working properly, particularly with any security features turned on.
So anyway, I'd recommend against 2Wire, even if it were cheap.