I know next to nothing about both of these amps but have an opportunity to get either for a very good value. RH450 From what I've read the RH has a lot of power and I love the flexibility of the eq section. Also heard this company makes the least noisiest amps of all. Also have read you can dial in about any tone you want with a little work even that of an SVT CL. Hmmm. GB STL-900 Lots of tubie tones but doesn't really hit the mark when trying to overdrive. Lack of tube power section may be the culprit. When pushed I've read where the low end gets saturated. EQ section is kind of "different" and would take some getting use to. Definitely rocks the house. The bad news is neither of these are that poplar in county and I'd be buying on blind faith - that where you come in. Not really a biggie because I'd probably flip it if I end up not being impressed. I just have always been a little weary of the whole class d amp craze. But I need a small basement amp and these seem to capable and fit the budget. Cheers.