Discussion about the Korg PolySix synthesizer

I've got two Polysixes now.  I've had one for a year, bought it, 
replaced the battery.  Also bought a Kenton Midi Kit for it but never 
had it installed, got it off ebay and it was missing the midi jacks 
and some of the installation instructions.  

Just bought another off ebay with Korg Midi kit installed (which also 
bumps the memory to 128 programs!).  The seller said the battery had 
leaked all over the inside.  Got it yesterday and guess what...the 
battery had already been replaced and there was no damage that I 
could see.  Everything seems to work fine except the output sound is 
terrible.  Seems like the volume is weak and sounds are sort of 
distored.  This one is in much better shape than my other one.

I'm not an electrician but I can do basic stuff (like putting in a 
coin battery and all that involved with that in my other Polysix 
although I didn't have to replace any of the traces.)  Anyway, 
ideally I would just like one Polysix with midi.  I'm thinking I can 
get there between these two synths.

Does any one have any ideas?  Worst case I'll hang onto it until the 
fall and probably send to to a tech.  I just got my Minimoog back and 
after spending $700 on it I'm not anxious to spend more on other 
synth repairs right now since I hardly ever play and just like to 
mess around with them.

Is there a part I should take out of the one and put it in the other?

The one I just got looks great (except the side have some dings), all 
the contacts work perfectly, very clean looking, etc.

BTW, I'm going to make some real wood panels and replace the crap 
laminate that the polysix came with.  I'm going to make two sets but 
could make more if anyone is interested, but you will have to pay for 
them.

Any help would be greatly appreciated.  I'm in the Cleveland Ohio 
area.