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?
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.