I hate to be the guy that bursts your bubble but your budget dont allow many real choices,new or used.If i were in your shoe's i'd save up a bit more,around $1,200 usd then you'll have some serious choices,new & used.
One thing ive learned is to try & not get off as cheap as possible when buying gear,others will freak out & say all amps sound the same blah blah blah but my reasoning is this,get what you want in the first place instead of getting what "you can" right now.
If you buy what you REALLY WANTED the first time around you wont want to upgrade again, if you try to squeeze a budget you wont be happy for long.