Much as I love my Tyros 3, and before that the PSR3000, I do almost all my sequence editing on a PC other than transposition (the keyboards understand megavoices better) and occasional revoice and level adjustments.

I'm thinking about getting an SX900 and whilst I believe that the sequencer has been improved it would need to be a pretty radical update to make a difference to my workflow, and I don't think this is the case.

Korg sequencer still way better for editing.

The SX (and (after a recent update the Genos) has a Chord Looper which is a type of chord sequencer.