Maybe I can offer my perspective on the comparison of the two units, since I just upgraded from Krell 400xi to Pass Labs INT-150.
Th Pass INT-150 is Nelson Pass' first foray into designing an integrated amp. It is essentially a X-150.5 stereo amp and a simplified version of the new XP-10 preamp. It runs in class A for the first 10 watts before switching over to class AB.
My initial impression? Well I am smitten by the sound. Let's get the negative out of the way. This is not the greenest of amp, it draws 225 watts of power in idle and 600 watts at peak. Although this amp is supposed to run 20% more efficient than previous design, it still runs pretty hot but not too hot to touch. This is all the negative I could find so far.
Compared to the Krell which puts out 200 watts per channel, this Pass is rated at only 150 watts. However, in actual operation, the Pass sounded like a much more meaty amp than the Krell. One magazine review rated the X-150.5 as having a 250 watts output at 8 ohms, so the amp is likely seriously underrated. It absolutely kills the Krell in explosive dynamics, high resolution and ease of flow and the Krell was no slouch in this department.
The amp has a lot of the legendary sound signature of all Pass products, like the Pass Xono phono preamp which I also own. It is warm, lush and sweet, with a deep soundstage and yet has details and tight bottom end to die for.
One of the nice things about having pure Class A for the first 10 watts is that you can listen to the system at low level and still get that gorgeous sense of musical flow and low-level continuity. When you crank it up, the amp really puts my Dynaudio Special 25's through their paces. The amp renders all instruments with an astonishing accuracy of timbre, liquidity and ease of flow. Dare I say almost tube like, but not many tube amps can produce the kind of dynamics the Pass amp can put out.
