A couple of points-

a). The Triton and Trinity both have crap factory acoustic piano sounds. However, I've not come accross any synthe (except perhaps a Kurzweil) that has nice stock acoustic piano patches (including Roland JV's and XP's).

b). Korg have a dedicated PCM piano/organ expansion board for the Triton which I quite like. I play (and teach) both piano and organ and I find the patches on this board nice to play.

c). New keyboards to check out with nice factory acoustic piano sounds- YAMAHA S80 and ROLAND XV88. Both have 88 note weighted keyboards to make playing these sounds just so much more satisfying (note- I hate playing acoustic piano sounds from an unweighted keyboard!).

d). Don't simply go by what you read on this (and any other) post and site, USE YOUR EARS and get into the shops to hear for yourself what sounds good or not! Everyone's opinions are different when it comes to this often senstive topic. Cheers.