Hey I think I just made my S90es piano sound better even in mono, and tons more punch.
Simply use compressor #2 -13.5db (or season to taste) and parametric EQ 4032Hz width around half. Regular Eq to taste. then fidgit a bit with the onboard EQ in the S90es.... seems to clean things up quite nicely. Of course you'll have to adjust to YOUR taste.. but I think this punched up things quite nicely for me. Let me know if this helped the piano dudes.
Dave

LOL... ive decided theres no workaround. Piano's are just gonna sound dullish tinny till I can think of a way of reverting back to stereo... maybe a keyboard amp as the right channel...I spent a lot of time getting my sound right.. and sorry to say.. the configuration of the bose just isnt conducive to stereo samples period.. cant have everything.

hmmm..... what about putting a bose 802 lll panarray beside the bose L1 or mackie srm350 three feet from the pole.that just might work

I would have to agree... I LOVE the bose system, however, I don't even play with it. I just have it in my living room to play music! LOL... BUT when I hook up my old Clavinova, it sounds great. So I am thinking it has more to do with phasing of these new keyboard. But again, I HAVE the piano sounds of ALL these new keyboards. I love a REALISTIC piano. Most of them have a vibe/tinny sound to them naturally.

I have a good ear. Unfortunately it doesn't work with pitch as much as it does tonal quality! LOL

Thats my problem... i became so sensitized to STEREO field...it sounded like my piano was 'sick'.. or cheap. I keep plugging the YAMMY into the KRK's just to make sure. My friend is gonna bring over his Mackie srm350 v2 to see if i can rectify the problems. I definately wont feel confident if I dont like the sound coming out. Im spending money i didnt have so I could have state of the art... kind of magical sound.. and it came real short. Guess YAMAHA , ROLAND , KORG... tune thier instruments to sound good in a recording situation... which is odd.. cause the S90es was made as a LIVE keyboard and certainly marketed that way. IF someone has the S90es or the like... try the second amp and see if it supports the L1 with the stereo issue. I'll give a report. MO MONEY MO MONEY MO MONEY damn. Luckily the srm350 is 24 or so lbs, and small.

Check out this approach (using Delay) as another means to 'tweak' stereo samples into a reasonable mono signal.