are there any portable keyboards out there with a decent (for an electronic keyboard) action and a good sound, with more than 88 keys? (for example 97 keys as on a Bosendorfer Imperial acoustic piano). I might like to get a keyboard sometime for portability to take with me places (including playing in our minivan while I'm going somewhere with my family) but I would be running out of keys on a Yamaha DGX-500 (and I don't like the action on it, the piano sound isn't quite what I like, and I don't need quite so many other features.)

WHY exactly do you need more than 88 keys? First an 88 key digital piano will not fit across the seats of your minivan? You will need to flip the seats down to fit one either way? As far as I know there is no Portable keyboard with more than 88 keys....Wouldnt be portable anymore would it? And running out of keys????? How many piano pieces are composed for an instrument with more than 88 keys? You could get a grear portable piano for not a lot of money i.e. Roland FP-2 FP-5 etc... Maybe I dont understand your question fully but....There isnt a maker out there....Perhaps a software based piano would allow for a longer range than 88 keys but again every one I have played with are based on sampling over an 88 key range...No offense but i think you should set that one on the wishlist and look for a good 88 key portable digital piano.

You don't know him, Pro. 88Key likes to use more than 88 keys. He loves those low notes.