Let's see:

Korg digital piano
Roland A-50 controller
Korg Karma
Oxygen 8 controller
Yamaha PSR-8000
Miracle Piano
GEM Bachman
Yamaha PSS-680
Yamaha SH10
Wind instrument with keyboard control
A few other toy keyboards (Yamaha and Casio).

The first four I consider "essential". The piano is used primarily for piano practice. The Roland A-50 controls my Roland XV-5080, taking advantage of polyphonic aftertouch. The Karma provides my autoaccompaniment and is used with the A-50. The Oxygen 8 is used to explore music software. The fifth, the PSR-8k, is at a second location and is the closest I have to an all-in-one solution. The others are mainly there because I rarely sell stuff or throw stuff away.

I don't see adding anything soon. I still have not returned to my house since the fire last summer. But next item is to upgrade the electronic piano. I would like to upgrade the Oxygen 8 to 3-octaves (it has two wo aftertouch) with aftertouch. A possible candidate would be the Nord Modular G2 announced for October. The Motif ES 7 (also announced for October) is being considered as an upgrade to the Karma. But as I have posted elsewhere, if the ES does not support chord inversions, I might pass on it (until it does). I will give the Korg PA1xPro a close look and am particular looking forward to whatever produces as their next high-end arranger.