The 5150 definitely has a lot of "bite", but not much else. They're VERY dry & thin sounding. They almost sound like scraping sheet metal to my ears after the novelty of it being a "5150" wears off. One of my friends bought one about 2 years ago, he tried everything he could to get a good sound out of the distortion channel, it just wouldn't do it. He still has it, but he uses distortion pedals instead of that thin lead channel. He just recently bought a 50 watt single channel Marshall JCM (800, I think), he's much happier with it (but he's still jealous of my Blue Voodoo's tone, hehe). Those Shefield speakers suck, too.
Try a Marshall head or Mesa triaxis preamp w/ a tube poweramp with a marshall Celestion cab.