What to put in 4 rack spaces?

[James R. Coplin]

So, my new main studio desk is finished and powered.  It has allowed me
reclaim a good deal of space in my studio (about a foot and a half) and
holds more than my old desk.  However, I have 4 rack spaces left over.
Depending on the final config either 2 two-space openings or 1 four-space
opening.  

My studio is in 3 parts:
1. The main desk which has the DAW, most outboard, audio interfaces etc.
2. The modular desk which has some misc outboard, MIDI->CV, the Serge,
Modcan and ARP 2600
3. A keyboard station with all the keyboards, Synth racks, and MIDI
interfaces.

I'm thinking of moving one or more of the synth racks from the keyboard
station over to the main desk in the open spaces.  I don't know why I'm
thinking about doing it, it just seems like it might be a good idea.  So,
what should I put there?  Here is my short list of options:

Waldorf Microwave I - 2 spaces
Waldorf Micro-Q - 2 spaces
Waldorf Pulse+ - 2 spaces
Korg Wavestation A/D - 2 spaces
Roland JD-990 - 2 spaces
Emu Audity 2000 - 1 space
Kawai K5000 - 2 spaces
Yamaha FS1R - 1 space
Voyetra 8 - 4 spaces

I use Sound Diver heavily so I don't know if it makes sense to move things
like the FS1R or K5000 as I rely on Sound Diver to program them because the
interface is so rubbish.  So, if you were me, would you put something in the
spaces from the synth racks or would you leave them all together in the
synth station?  More importantly, what would you pick and why?

Thanks!

James R. Coplin