used peavey combo 300's hover around 250, and used matching 115 cabs go for around 100. that's about 350 bucks for 300 watts into 215", leaving 150 bucks to spare.
that's a kinda big, somewhat heavy rig, but loud and oodles of eq (iirc, 7 band, sweepable mids, and pull-deep/bright)
the 800rb mentioned is a workhorse, and right up your alley for metal tones (a good reference is "appetite for destruction" for this amp's signature tone), but it's a head, and you'd still need to get a pair of 8 ohm or one good 4 ohm cab.