The most common fix for aluminum wiring is to have it "Pig Tailed" the electrician refits the terminating ends with copper. This leaves the aluminum in the walls in place. The concern ,as mentioned, is the brittle wire. But since the wires in the wall are stapled and not prone to movement it can usually remain undisturbed. At the ends where it most likely to me moved it can break or crack the replacing of the ends with the copper which is much more plyable reduces this considerably. As far as the sonic differences between copper and alum I doubt that there is much. If possible run a dedicated 20 amp circuit(copper of course)to the outlet for your system.
Aluminum wiring
I recently moved into a house with aluminum wiring and am considering converting over to copper. Is there a benefit to converting for sound quality?