Ugh, so I'm looking to trade in that piece of crap MG250DX sitting in my room, because at the time, my ignorance on amplifiers was blaspheming at best, and so I thought, "Marshall, big, OMGAMAZING." Idiocy doesn't go a long way in the world of guitars.

So, I'm trading it to the store that I bought it from, and in order to get the best deal, apparently I have to trade it for a $600+ amplifier, otherwise it'll only be a "standard trade" or whatever. I bought the MG for $500, so I'm not quite understanding this "best deal" thing, but if I'm getting a more expensive amplifier by trading in a cheaper one, I'm not looking to complain.

Regardless, the price requirement kicked the Peavey Valveking series -- apparently he gets the 212 for cheaper than $600 -- out the window, and now I'm looking for some all-tube amplifiers within the $600-700 price range.

I dig Dream Theater, possibly a bit too much, as well as Metallica, Megadeth, Ozzy Osbourne (Rhoads years), and I'm basically looking for tones within the progressive metal/heavy metal style. I looked around on some websites (musiciansfriend, zzsounds, et cetera) and saw some decent-looking ones, but I have no experience with them, so I don't know what tones I could possibly pull from them, thus, I'm back to square one.

Any suggestions, my horde of fellow axe-slingers ?
Peavey Classic 30 is right at $600. I would sell your mg on craigslist get more for it, stores will only give you 25-30% of the new price for trades so they can make a profit off the resale. The store will make profit off you twice.
Epi SG G400 Lefty
Modded Valve Junior
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Toneport GX
The Peavey 5150 II produces some solid heavy metal tones, and if you look around you can probably get one for $650-750. I found it produces more of an 80s metal tone, which is really nice...but if you crank the pre up to 5+, you'll get some insane distortion if you need it
You should also take a look at a Traynor YCV50 Blue. People say it is one of the best amps for the money.