I like the 5150 tone, but the ones I've tried are too noisy and not very reliable
I had a 6505 head and felt the same way about the noise. I never had reliability issues but I didn't tour with it. There's a simple mod floating around that will tame the noise and make the gain control much better behaved. You simply swap out one resistor in the preamp:
R9 is a stock 1M resistor (same value Soldano uses but the Soldano amps aren't this noisy). If you lower that a bit is will quiet the noise and actually make the gain control more useful higher up the dial without sacrificing the aggressive tone. You don't even have to pull the main board - the resistor is on the preamp board with the preamp tubes so it's very easy to access. If you're handy with a soldering iron you can be in and out in 30 minutes or less. I tried a few values. I actually tacked in a 1M pot and played it and adjusted it until I found my sweet spot which was 330K and then I soldered that resistor in place.
It won't turn a 6505 into an SLO 100 but it makes it a little smoother and a little more SLO-ish. When I sold the amp the buyer said it was the best 6505 he had ever played and I believe him. I hope this helps someone in the future.