If you can find Gatorskins on the cheap, that's not a bad way to go. I've commuted and light toured on 700x32 Gatorskins and they worked well for me. Of course, it's what you're using now, so I don't need to tell you much about them. It appears that 700x32 is as big as they come, and they'll almost certainly cost more than $20, but they'll probably last longer too.