If you want to move up a little, then a decent multi-effects processor is a better investment. The Boss GT-8, the POD XT Live, or the Digitech GNX 4. Any of these will run you between $400-500, and you can get very workable tones out of them. I bought the GNX-4 and it sounded o.k, until I bought the mfx supermodels 'Metal' pack. www.mfxsupermodels.com The models are very deep, rich, and absolutely crush - I've never gotten sounds like this out of a unit.
Most effect units or multi's sound a little thin and digital, but will work. If you want to spend a little more, say under a grand, you can, with a little searching still find decent tube head/cab combos. You won't get a Boogie or a Bogner. You can get older Carvin tube 100w heads (the X-100B model) for around $400. I owned one for a number of years and it has great distortion and versatility. You can get an older Marshall JCM 800/900 combo amp for well under a grand, and of course it has great tube tone, and 50 watts is plenty to play most small to medium size venues.
Just remember, buy something that is a great value and sounds great, not just because it has a 'name' on it. You don't have to have a Boogie or Marshall TSL to have great metal tone. Spend you money on a good guitar instead.