I know I'm getting into this way late, but I'm having trouble picturing your setup. So you've got an integrated amp with 5.1 inputs, right? It does no processing whatsoever. So the only processing you're doing is in your SACD/CD player? How many speakers do you have? How is the SACD player hooked up? Does the integrated amp have provisions for crossovers for the main speakers? If so, then it's doing processing. If not, you're in my old condition, where I was actually using tape-outs to supply signal to my sub and using the sub's crossover. Now, I didn't have this setup with really good speakers, but it seemed to work.
I find that a sub can enhance music quite nicely--even with M80s, which have substantial bass of their own.
And yes, there were subs before HT.
