The Nitro is a bad ass amp. I used to own one with EL34's. I know people like to rave about how good they sound with KT88's, but I really couldn't imagine it sounding better than it did. To me, It was everything I wanted my 6505+ to be. I never even boosted it. I can only imagine how killer it sounds with the 33.
I went back today and bought it EL34's. It really came alive running it through my Mesa cabs loaded with V30's. The one thing I do recall is the Splawn cab I owned with the small blocks sounded great.
I have my splawn quickrod for sale, but it absolutely rips with my 33 pedal. if I didn't have amps laying everywhere id definitely be keeping it. I personally love the 33 pedal, but it is finicky with what amps it works with. splawn has always made killer amps.