As I mentioned before, I wouldn't expect a RK to sound like a Stiletto, but there's something wrong if the only sounds you can get all sound like a Dual Recto.
It's always interesting to read threads like this about the RK. The RK is a very tempermental piece of equipment, as you can see from the myriad responses.
That being said, I've spent countless hours tweaking my RK (I virtually stopped practicing for 5 months, and allocated all of my practice time to tweaking my RK). I'm glad I did, because I can now do anything with my RK.
Some of tones that I am most proud of accomplishing are:
1. Mark IIc+ Rhythm
2. Lone Star Clean (the piezo/electromagnetic pickup combination on my EBJPMM probably gives an advantage here).
3. Lush, harmonic Rock sag (for lack of a better description).
I use a RK head / RK 4x12 / John Petrucci Music Man Axe. No effects (except occassional reverb on the RK, which sucks by the way).
I'm not going to post my settings here, but as an example of how sensitive the RK is, consider that if I change from spongy to bold, then my c+ sound goes straight to hell. Likewise, if I change to a different speaker selection, or if I switch the power section, then I loose the c+ sound.
You have to be patient with your RK, and you have to carefully taylor your settings to your own equipment (if I use my Ibanez with the same RK settings as my EBJPMM, it sounds completely different).