I like DSL's, I will be picking one up again at some point. They do,however, need to be LOUD to get the best out of them. never tried it with a boost though, but still want to own one (along with an 800
)
Anyway, second hand you should be able to score a 5150 II or 6505+ quite easily for that amount of cash
Otherwise, I'd recommend keeping an eye on ebay, as occasionally some good stuff comes up. Don't discount the marshall jubilee and anniversary heads either, avoid jcm900's.