xstatic is correct. if it uses op amps ...look at the op amp and it will have a marking as to manufacturer. then what you want is to contact people like analog devices, Texas instruments, linear technology, and maxim and others
(search google for op amp manufacturers) and find out what they would recommend as a better drop in replacement but with no change to the
circuit characteristics. the key words are DROP IN REPLACEMENT with better noise spec. then try just one channel and hear if there is sonic improvement.
sometimes there might be an improvement - other times not.
you might also try newsgroups like in google rec.audio.pro and see if you can find people who have successfully upgraded the soundtracs , and what they did technically and the cost involved.
peace.