Up for sale is a mint condition UB-Xa (only listed as "excellent" since I don't have any stickers on it!) I'm the original owner, haven't had this long, and it's never left my house. No flaws in appearance or in working condition. This was an impulse buy--I got it thinking I'd make it work in my gigging rig, but the reality is that I need piano/rhodes and organ far more than a nice synth for my band.
Please research what this can do, and what it can't. It's a faithful recreation of the Oberheim OBX-a, with additional modern enhancements like multiple "vintage" modes and polyphonic aftertouch.
Included is a bank of Synth King patches that I bought even before the keyboard arrived. I'm unable to include the link here, but search up the 'tube link. They really show what this keyboard can do.
I'd be glad to answer any questions you may have about the keyboards--pros and cons, and help you decide whether this would be a good fit for you!