SPD-S uses 16 bit 44.1 kHz files - that's CD quality.
Good point. I feel the SPD-S has pro sound quality for the tasks it was designed for.
If someone is having issues with the sound quality it's more likely the sample itself or that they are hearing it through less then stellar equipment. In that case, better samples and better monitoring/sound gear should be the main targets. You can bring in your own samples to replace any of the ones on the SPD-S and many do.
If you want to step up the sound quality further, you need to look at software based instruments and a DAW interface with high end outputs.
And the questions should be:
1) - Why am I spending that much more money (to get 48k/24bit or higher sound)?
2) - Who does it matter to and can they hear the difference?
Although the SPD-S
can be used as an electronic drum kit, I don't believe that it shines in that capacity - nor has Roland positioned it so. If you want a good electronic drum kit then look at the middle to high end V-drums (TD-12, TD-20, etc.). Yamaha as well.
If you want the best electronic drum kit available, buy a Roland TD-20, don't use the internal sounds and trigger DFH Superior 2.0 (or BFD) software using a computer running Pro Tools, equiiped with a Digi 003 and the outputs run through a good PA or straight (virtually) into a Pro Tools session for recording.
IMO the SPD-S is not a professional drum set replacement tool. IMO,
any electronic solution, no matter how high the quality, won't be the same as a great drumset with good heads tuned well and played by a professional in an excellent recording environment (good mikes, good mic pres, good room, etc.).
The SPD-S is a great instrument for so many other things. Just watch live videos of acts using loops, background tracks and homegrown samples and you'll usually see an SPD-S next to the drummer or percussionist. You just have to understand the strengths and limitations to use it properly.
HTH
Jim