As you've probably already noticed with pros, Fender tube amps are extremely popular, to a great extent due to their stellar clean tones. And since they're popular, the used market has a lot of choices. I'm thinking maybe a Blues Junior (15w), which can be had for about $300. Or, for a bit more ($450 or so), a Hot Rod (40w).

As for "blowing the tubes", heavy use may shorten their life, but I wouldn't worry about that. There are also many fine solid state amps to be had, and $300 will go pretty far - Roland cleans are highly regarded (I have a Cube 30X, and I agree).

Maybe Frankenfretter will chime in regarding his Roland Cube and use of pedals.