Pass xa600.5, Marantz 9S2 or Mcintosh MC501/MC601?

Another vote for he Pass Labs.

I have Tyler Acoustics Linbrook Signature system speakers with a Pass XA30.5. They are definitely a synergistic match for each other. At higher volumes (90db) the needle moves past noon, so at some point I'd like to move up the line and get a more powerful Pass amp.

I can't comment on the other amps because I've never heard them.

I owned the Marantz and found it to be too polite. I own Pass now and have no desire to upgrade my amp anymore, having been through 5 amps, some a lot more expensive than the Pass. One was a McIntosh, which has a warm mid-range but somewhat flabby bass.

IMO..having owned all three makers..Pass Labs without a doubt

I think this comparison isn't correct---does the OP really mean XA60.5? 600.5s are much higher in cost than the other alternatives.

On McIntosh, Mac 601 doesn't sound like a 402 or set of 501s at all. This is like comparing Pass X250 to X250.5 imo. Totally different amps.

I've owned X250.5 and Mc601- both are great amps, but sound very different so speaker match is more the thing here (and I've never heard Tylers)

The point that the amp should really work synergistically with the speakers is a good one. Does the OP have any further comment, on what he tried, for future reference.