The biggest upgrade you could make would be to ditch all of that signal processing for a good two channel integrated amp. A lot of newbies think they like the gimmicky sound fields, but once you’ve heard two channel done right, you won’t worry about all that hokey stuff.+1 @ozzy62
This is my thinking as well after looking at your system. Forget the TT & get a proper preamp. If you like the DSP over your Sansui C-2101 preamp its a good indication that the caps (among other things) are dried up. IF the caps haven’t been replaced in the amp, get it recapped as well. As others have said, your existing TT matches the system. New caps in amp and new/used preamp will improve that TT a lot.