I purchased a used MAG300 about 5 years ago when I needed more oomph. I still use it regularly, and it still powers my 4x10 with enough juice to keep me heard about a loud drummer.
The EQ is great, and the low and high boosts are a welcome addition when you need 'em for that little bit extra for a song. I personally haven't used the subharmonic feature, but these things are built like tanks. It's been outdoors, it's gotten caught in rain, and it's been bounced around car trunks. Can't ask for much more out of an inexpensive head.