Spectral vs Pass

Has anyone heard both Spectral 200/250/260 and Pass XA 100.5/160.5 on Magnepan 3.7´s? Heard the Spectral DMC15/DMA200S on the 3.7´s and really liked what I heard but I have never heard the XA-series on Maggies. How do they compare? TIA
I can't answer your question directly, I'm not that familiar with Pass and have not heard either with Magnepan but I am very familiar with Spectral and since you aren't getting much response I'll offer what I can.

I have been around Spectral for many many years and they are without question my amp of choice. I have owned the DMA 180, currently DMA 360's and am about to acquire a DMA 260. What you get with Spectral is the ability to articulate better than most amplifier designs...speed, clarity, lifelike imaging and amazing dynamics. I have yet to experience any other amplifiers that can reproduce recordings as Spectral can although I'm sure there are a handful that can. What you also get is an amp that can sound terrible if not matched with the right pieces. They amplify EVERYTHING. If your power is not correct this alone can cause a mess, from my experience. You need to take great care in selecting power cords, how your power line is set up and possibly even conditioning. Cables also become much more important than other amps. You must use MIT cables and even within the MIT/Spectral lines there are some that sound great and others that sound not so great. Lastly is ancillary gear which again must be selected with care or the end result will not be satisfying. To start, you must use a Spectral preamp. There are some who do not and a very small handful of other devices that can drive them (Berkeley DAC is one I know of and use) but Spectral requires it for warranty and clearly recommends this for best performance (Spectral pre). That sounds like a long list of stuff just to get an amp to perform but for me, it is more than worth it as the end result is a pretty unique ability to reproduce source material with accuracy and precision just not available in most amplifier designs.

Both are amazing amps but they are also very different in design and presentation. If you absolutely love Pass, you may not be crazy for Spectral and vice verse. If you are not into really working at system setup/design then Spectral may not be the best choice.

Good luck on your search and let us know what you find out along the way....
Have had some experience with Magnepan 3.3's. I was using my dma-90's bridged with output of 180 w/per channel, and couldn't flesh out the bass from the Maggies. The dealer lent me his DMA 150 at 150 wpc, lower wattage, but higher current and the sound was wonderful. For Maggies, go with brute strength for the dollar,such as older McCormick, or Bryston amps.