If you really want to play, explore your options.. and then just go get something that you think will work for you. The equipment itself is important to a point, but there is more to it than that. The player behind the equipment is the most important part for me. If playing whatever you have in front of you seems like too much of a chore, then maybe it isn't meant to be, but I think you really do want to get something and play it Paul.
I agree with Ed. I played keys long before I ever got my first arranger. Having a modern arranger though has been beneficial to me in that it has allowed me to learn to play along with an electronic back up band in genres of music that I had not played in before, which expands my abilities as a player. It's also a tool that allows me to better express myself and my music in a live setting when I can't have a live band with me. The tradeoff is that you won't find many arrangers that have a detailed synth engine for making up those cutting edge or off the wall synth sounds.
I have the Korg PA80, and it is among the best of the arrangers out there for editing sounds. It allows for sampling ( with an optional Korg formatted smart media card ). Still, if your focus is set on making abstract sounds, then an arranger is never going to be the best choice. I like playing with abstract sounds at times by the way, but more often than not, I want to play or make music, so I use the PA80, my Motif ES, and a few soft synths. You have to decide what your priorities are and then make a decision. If you wind up with something that really isn't your thing, all is not lost, as you can always sell it later on.
AJ
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AJ