Well, I have to say quality wise, cheap crate's and marshall suck. A friend that fixed amps saw alot of these come thru his work...cheap crate is real junk, marshal sounds ok, but still not the greatest quality. Marshalls big thing is there cabinets sound good.
Don't know much about HiWatt, but arn't they more than $300?
I hate to say this, but for cheap, Peavey is hard to beat...I have seen there chorus amp for what you want to pay, and they have some ok tube amps that ya can find for your price.
Myself, I like tubes so I have a Rivera amp. If you keep your eyes open, maybe ya can find a used one in you price range....maybe.