The SY99 is very deep and powerful.

It wasn't a very popular synthe, not because it wasn't good(!) but because it was very expensive ($6,995.00 Aussie in 1991).

The SY99 had a similar fate to the Korg T series instruments. The SY99 is basically what the older SY77 should have been in the 1st place and the T series (T1,T2,T3) are what the Korg M1 should have been in the 1st place! Both the SY77 and in particular the M1 were successful, but the T series and SY99 weren't- mainly down to price and the fact that other much cheaper synthes were coming out at the same time! These cheaper synthes were not always better though- just the latest 'flavour of the month' synthes like the Korg O1WFD and Roland JV80.

I would hold on to the SY99!!!! Just because you are using are slightly less popular synthe shouldn't make you rush out and buy the hottest thing with keys just for the sake of it!!!!

If your music sounds great, your SY99 is certainly kicking butt!! I'd use that fantastic keyboard as a master controller also (it is a great controller!!) and add extra modules like somthing like a Novation Nova or Clavia Nord Rack and a Sampler. Boy what a set up!!!!!!!!!!!!!

You are lucky to be the owner of an SY99!! Cheers.