Thge Pass X150 should not be mistaken for the Aleph series of amps produced for several years by Pass Labs. The Aleph series was built by Pass, the X150 is outsourced for the most part. I had one and the heatsinks are cheap and thin, the IEC P/C socket was loose due to the screws being stripped and the sound is nowhere near the other X amps or the Aleph amps and should not even be compared to the Levinson...with your rig the # 334, 335, and so on would be a great addition. Build quality is superb, the sound, once fully broken in is excellent, and the resale value extremely high. Notice that the X150 sells used for the mid 2k range, while even older #331 amps from Levinson sell for 2.5-3k. Mgl123's report on the Aleph 4 is very accurate, between it, the Aleph 1.2's and the 2's, it would be a coin toss over a levinson, it really matters what is in your system in addition to the amp. The X150 is a horse of a different color...one which I believe would end up sounding more like an expensive millstone...
