Lucky2Bhere,
I have tried to answer most of your questions (both on the forum, via personal emails and on the phone). I am still not sure of what you're looking for but here are some guide-lines..
Ketron SD1Plus/SD1Plus EXP:
Best Natural sounds (over 300), Great styles with authentic drums and bass (over 300), Sequencer (you can make your own Midifiles from scratch track-by-track), Sampler (you can record your own sounds - also these new sounds can be used in the sequencer or with styles, Vocalizer (you can add harmonies to your voice or whatever instrument is plugged into Mic1-input), over 6GB Hard Disk (you can store thousands of midifiles, wave files, styles, user settings, your creations ...etc) [EXP adds a further over 30 new samples used to generate over 40 new sounds (some used wiht the new styles - especially the converted ones so they sound exactly as they would from their original keyboards), over 700 new styles], and 76 semi weighted keys.
Ketron XD9/XD3:
Similar to above BUT (XD3 is Module version of XD9); less sounds, less styles, no Sampler, no Sequencer, optional HD and vocalizer, 61 keys (non weighted), speakers (XD9), Pattern editor (for creating your own styles ... also found above). EXP is same on this (just less sounds).
Midijay - Player.
MP3 and Wave playback (wave recording), loops, grooves, and styles as well (about 170 styles plus exciting audio grooves that can be synced to the style. Lead mute used on midifiles and wave files, audio file transposition and pitch change (in real time), arranger (can add new styles to HD but cannot create new styles on Midijay), voice editor [Remember the pattern editor and voice editor are not as full-blown on this as the previous modules above], very light and can be used with any GM controller.
My suggestion.
For live performances and use on stage - SD1Plus/SD1plus EXP (if you want to feel as though you have 4 keyboards in one).... if budget is an issue, the XD9 will do.
If you already have another keyboard and just want the Best Natural sounds and styles of Ketron, then the XD3 would be for you. However, if you want to have audio playback capabilities and do some "DJ" work yourself while you are on break (hence eliminating the need for your employer to hire a DJ as well), then the Midjay will suit this purpose in place of the XD3.
For "Stage sound quality and Live styles" or live feeling, you can count on Ketron products to do a better job. For CD quality (synthesized sounds and studio mixed sounding styles) feeling, you can count on many other brands that do a better job at delivering such quality.
This would be my input with regards to what you're looking for.
Everything I have mentioned above doesn't in anyway replace you spending some more time on the products BEFORE purchasing, which is why I have invited you over to the labs when you get a chance.
Thanks,
AJ