what are they used for? i am a pretty basic piano player, just using the 88 keys and the damper pedal. was wondering should i get the px-5s but not sure what those 2 wheels are used for? do many people use them?

You most likely won't use those wheels for normal piano playing.

The pitch [bend] wheel does just that -- raises and lowers the pitch. Kind of fun, but more of a synthesizer function. Same goes for the modulation wheel, except it may modulate an LFO (Low Frequency Oscillator) in order to produce vibrato, or to control the speed of rotary speaker emulation for organ patches. It may have additional assignable parameters as well.

Again, not so useful for piano, but if you get in to organ, strings, synth (lead) sounds, you may find those controls more useful.

http://www.sweetwater.com/expert-center/glossary/t--PitchBend

http://www.sweetwater.com/expert-center/glossary/t--ModWheel

Kawai James will be happy to read that there are piano players who don't know what they're for. ;-)

Picking up on what LC said, a pitch bend wheel is commonly used when playing, not just synth sounds, but also the sounds of instruments where players often bend the pitch (for example, if you wanted to create the sound of playing lead guitar, some violin effects, etc.), you are creating pitches that are in between those that can be played from the keys. The modulation wheel is, again, often used to introduce vibrato, but it can introduce many many other kinds of effects as well, depending on the design of the keyboard. They are not used for standard piano playing.

If you're just interested in piano, the PX-5S will have a whole lot of stuff you won't need. That said, it still might be a perfectly good piano choice, as the piano (and especially EP sounds if you care about them as well) look to be improved over the PX-130/PX-350.

Anotherscott - not sure if that is true. Did not Mike Martin state in a couple of the NAMM videos that the PX-5S shares the keybed AND the sound samples of the PX-350? Or have I got this total wrong?

The PX-5S has MANY samples that are not found in the PX-350 including some that have never been in any instrument before.

Specifically new on the PX-5S:
All new rhodes, wurlitzer, clavinet, harpsichord and acoustic bass (There may be others but those are the primary ones). There are also many other samples that are brought over from the XW-series synths.

Sorry, Mike. Didn't mean to present a negative view. What I intended to say that was that the piano sounds are the same between the two (the 5S and 350). Do I have that correct?

The 5S at least has the enhancements that were in the higher end 850 (string resonance, lid simulation, 256 polyphony). Whether there are other differences or new variations on the PX-350 piano sounds, I don't know. Probably at least more editability that may allow you to tailor them a bit more to your tastes.

Should that be "Specifically new on the PX5S"?

I have a pitch bend wheel on the CDP200.

The thing is it is spring loaded, therefore you can't really play and pitch bend at the same time lest you use your face or foot to bend it.

That's how almost all pitch bend wheels have been since the dawn of time (MiniMoog being a notable exception, though I think they invented the thing). It is meant to be used for one-handed playing. It's not designed to be a transpose device, it's a temporary effect. If it stayed where you left it and didn't spring back, you'd just have to bring it back manually, as otherwise you'd be playing out of tune.

Yes, my mistake. Fixed.