pic first I'll make this quick. Its a great poweramp. Again, impressed due to its size and the fact that its class D (I'm starting to learn class might not actually matter). I wish I didn't return the PB100 in order to buy the PS170 because I would have loved to have tried them side by side. Lets talk volume. This power amp gets much louder than the MosValve, just like the PB100 but, the PB100 wins the "Volume" race out of all three by a mile. That thing gets scary loud. Lets talk controls. The controls behave more to me like having an eq in the loop than having an actual presence/depth control which isn't necessarily a bad thing. I like that I can slightly scoop the mids. It sort of reminds me of what the "v" shape eq on a Mark does. The high knob is cool but, not as good as the "presence" control on the MosValve and definitely not as good as what the PB100 does. The bass knob I actually find to be more useful than the PB100 resonance control. Again, overall the controls remind me of having an EQ in the effects loop of a head. Overall sound quality? I'd say its on par with the PB100 and both will satisfy whoever chooses to purchase them. Both of them beat the crap out of the ISP Stealth Ultralite and the Rocktron Mainline IMO. PB100 vs PS170? I personally was slightly more impressed with the PB100. Its treble/presence control was just really nice. The PS170 is going back and I'm just going to stick with my MosValve. I don't want to sound snooty by using esoteric/edgy adjectives but, the MosValve just has a more "musical" quality to it, and the overall clarity is just refreshing/easy to listen to. Maybe it just really likes the combination of speakers and preamp I'm using? Not sure but, I dig it a lot. NOTE: Take everything I've said with a grain of salt. Don't be afraid to try the PS170 if you find a good deal on one especially if you want to do an "all pedalboard" setup. Its still the best power amp I've tried in its size range and in a live setting, I think you'd be hard pressed to hear the subtle differences I described above. At this level, we're all just nit picking. The Ps-170 is a real-deal heavy hitter in a small box and I would gig/tour one over the MosValve for its size alone. (Not that I'm good enough to gig or tour lol).