Hi!
Unfortunetly every sample playback synth with on board ROM waveforms is made for an "average user", who needs a bit of everything and isn't as "picky". That's why most guys (who need bigger samples and less junk that they don't need) buy samplers or workstations with sampling capabilities.
Some synth manufacturers like Roland and Kurzwell make expansion cards, but I prefer a 300 meg string section to a 4 meg one any time a day - that's why I use samplers.
ED