New McIntosh system problem... need advice

I've just assembled a new Mcintosh system consisting of a C220 and and MC352. I was replacing my old Arcam alpha 7 integrated amp, which has served me well, in preparation for upgrading my B&W DM602 speakers to something larger (probably B&W 703 or 804). I have kept my Arcam alpha 9 CDP.

My problem is that I don't feel the extra $6000 of amplification has actually improved my sound. The midrange, and especially low-range frequencies definitely have more weight and richness, but the higher frequencies are really lacking. In comparison with my Arcam amp, there is very little detail or clarity in the highs. This deficit is as dramatic as the improvements in the lows.

Does anyone think think this is typical? Is this the "tube sound?" I'm using the same cables when I A/B with the Arcam amp, so it's hard to imagine the problem lies there. Could I have defective gear? I bought it gently used, so I can't really exchange it. I would love to get some input on others' experience with these components, and also advice on which of the two amps might be more responsible for the problem.

Thanks!