I own the INT-30A, have not heard the INT-150. Mark at Reno HiFi strongly recommended the 30A for my comparatively quiet listening habits, and I've been very pleased. But I assume Pass makes both models for a reason, and each involves a distinct set of compromises (see the detailed review of each in 6moons). In particular, it wouldn't surprise me if people with large rooms, thirsty speakers, and high volumes had "power issues" with the 30A. Here's a little test I did (from another thread):
"Just compared my new INT-30A (basically the 30.5 boxed with a minimalist pre) against the INT-30A pre-section running an Odyssey Dual Mono (180wpc) as amp. Speakers are 92/4, room 14x20 in an open plan. Obviously, "synergy" favors the INT running as intended, and it did sound conspicuously better than the combo with the Odyssey: more air, richness, texture, detail, etc. *Except* that the combo had conspicuously more authority on the lows. I listen to mostly "small" music at lower volumes, and I'm sold on the sweetness of the Pass, but I concluded that those who say many listeners will want more power than the 30 are likely on to something."
At present I'm very happy with my decision, but I doubt the difference between the 150 and 30A (or the corresponding separates) is a coin flip.
Enjoying the simplicity of an integrated, btw.
John