Okay I Bought the Magnepan 3.6's

I should know, I have one and use it myself with my Maggie 3.6's. Really plenty of power, and the sound is, I think, superb, not much different than, or maybe identical to, the Pass 250.5's.

The thing with the Pass 150.5 is that it's not really 150 wpc @ 8 ohm. It's really like other manufacturer's 250 wpc amps. Explanation: Hi Fi News, the British mag, when they reviewed the Pass 150.5 about 2 years ago or so, found that it clipped at 8 ohms at 270 wpc!! Not 150 wpc. And, at 4 ohms, it clipped at close to 400wpc. I may be off a few wpc in my memory (I have the review someplace here) but not by much.

I use my Maggies in a reasonably sized room and barely have the amp turned up. My friend had the same set up - 150.5 with Maggie 3.6, and felt it was a great match.

If you try the 150.5 and for some reason want more power, you can sell it very quickly on A'gon.

I think the Pass 150.5 could definitely do it in your room. Depends on how loud you play your system. The difference might come down to the fact that the 150.5 would be out of class A into class AB, while the 250.5 might stay in class A, though if you play loud the 250.5 would also be out of class A.

Hard to say more than that, unless you had both amps and did a direct comparison.

Don't get pushed by some of the above posts into thinking you must have 350wpc, 600wpc, 1000wpc, 1,200 wpc. And the post above misstakes my experience that the Pass x150.5 was inadequate - wrong!

Of course, if you want to spend the $$, then you can't go wrong with a higher powered amp, other things being equal.
But, as I said above, it depends on how loud you play the maggies. The Pass 150.5, as I said above, is really a 250wpc amp disguised as a 150wpc, as per the Hi Fi News tests and is much more than merely adequate.

My 150.5 has more power than my prior Classe CA-201 (stated as 200wpc). My friend's 150.5 had, in his opinion, more power than his prior Classe CA-401 (400wpc), particularly in producing deeper more powerful bass than either of the Classes, which both of us felt were somewhat on the soft side on the bass. The Pass was better in all other categories also - detail, transparency, etc.

But, if you are unsure about the 150.5 and want to ensure adequate power but not go overboard on the power/price issues, I would say you can't go wrong with the Pass X250.5.