Take a look at Traynor's line of Custom Valve amps. Most of them use 5881/6L6 tubes and are a great value for blues, rock, and hard rock. They're certainly NOT metal amps though, if that's what you're looking for.
I can't believe how the prices of these amps have skyrocketed since I bought mine! I got the 80-watt 2x12 3 or 4 years ago for less than $600 shipped. Now the 40-watters are going for $750!
They do make a 20-watt version, maybe that one would fall into your price range. But I'm not sure if it uses 5881/6L6 tubes or EL84.
The Peavey ValveKing falls into your price range and it's a 6L6-based amp.
Also
the Peavey Windsor Studio 20-watter says it will accomodate 6L6 tubes, amongst others. It's $400 new at MF.com.
I've never heard of this amp before, but I just stumbled across the Peavey Vypyr 60-watter modelling tube amp. Reasonable price, 6L6 tube power section, plus all of the modelling mumbo-jumbo that's so popular nowadays.
Well, hopefully this will at least get you off the ground in your search for the right tube amp for you.