Well, if you want to have arranger capabilities for live performance, then the best option is to keep the I30 and buy the Motif ES. You can set up I30 and Motif via midi to play arranger functions in I30 and use some (or all) sounds from the Motif ES. For example, if you like guitars from Motif more than I30 then setup motif to recieve guitar channel from I30 and have best of both worlds.

If live performance is not a priority, then you could switch to soft synth type arrangement, but I always find software synths more cumbersome to use than the hardware stuff. I also like to have an arranger and a workstation to complete my setup.

As far as latency, it really depends on your computer setup and the kind of audio interface you are using. If you have a decent computer with a recent audio interface (something that supports ASIO or WDM) then latencies are pretty low and un-noticeable.