Just from what i have read from the forums here as well as stereophile, etc. the ML-335 is a much better amplifier and is a significant improvement over the #332 that it replaces. the early problems with Harmon regarding servicing your amp are not quite as bad as they were when ownership changed, but you can call to verify this... also, some people prefer the #334-5-6 over the #400 series as far as deep bass is concerned; a levinson 335-336 will outperform the PASS XA AMPS in the way they produce everything on the recording from the deepest notes to the highest effortlessly and with stunning dynamics, so the Pass XA's do have some drawbacks in spite of their excellent sound. also IMHO anyone who thinks they need a BIAS meter on the front of their amp or two layers of aluminum plating is not focusing on sonics. I would rather have an (old) PASS ALEPH 1.2 pair which sounds amazing without all of the latest gimmicks.
anyway, the ML-27.5 doesn't throw a 3-dimensional stage like the later ML offerings (i know, i owned a 23.5 which was a great amp for its time). you might also consider a rowland model-6 which has a "warmer" sound and plenty of watts.
an XA-100.5 is still around $10k used- anything less than that cannot
compare to a ML-335 in the ways i mentioned above.