Originally Posted by sterilium

Given the space that you have, I best thing I could suggest would either a Casio Privia or M-Audio Pro Keys 88 hooked up to your computer via MIDI with an awesome sounding plugin, such as Native Instruments Acoustic Piano. M-Audio is easier to hook up to a computer as it supports USB but can also be connected via traditional MIDI; you just have to make sure your soundcard is also good for the purpose like the M-Audio Delta series.

You might want to try Yamaha Clavinovas (the later models) or a Technics PR series (Has awesome piano samples that could knock the socks of those from Roland, poor polyphony though around 32 to 64 voices).