Which modem was $140 out of curiosity? I'm using the black terayon docsic modem (and have since june 2000) and have haven't had any problems with it. There were a few outages (once every couple weeks I could tell), but things were usually working within an hour's time. You don't want to skimp too much on a cable modem.
Keep in mind that this is a piece of hardware that will be on almost 24/7 (in my case) and should be designed to handle this kind of usage.
I went to The Wiz to sign up with Optimum, with a 2 year contract, the modem was $120 if my memory serves me correctly.
Hey, $140 isn't that bad. In 1997 I paid about $170 for a supraexpress 56k modem which doesn't even work now (got fried somehow) and didn't exactly provide much of an improvement over the 28.8 FastMac v.34 modem I had used prior.
I don't know about airport, but it should work work without any major issues. OOL works using DHCP, which airport works fine with for establishing IP addresses.
Once you go cable, you don't want to ever go back to dial-up.
