FWIW, I have three receivers with Audyssey and the difference between XT and XT32 hasn't really show up for me. THe sub tweaking and ability to tweak two sub channels independent of each other is more valuable to me than the filter resolution.
Granted, each of the three systems are totally different, but my oldest XT receiver used to be in my theater with the same subs and it did a great job. Everything sounded very good.