I saw that the new version of the Sampletank 2 will respond to the MIDI program changes. Here is the quote: "SampleTank® 2 sounds can also be associated to MIDI program change with one easy one click. This allows for instant recall of sounds during live performance, and makes it easy to build your ultimate General MIDI set."
Sampletank 2 is not cheap but the sound quality should be better than Soundfonts. Maybe it could provide another alternative... http://www.sampletank.com/Main.html?sampletank2-desc