I definitely want the MS6 more. But the MS3 is $3k cheaper. They both have their pros and cons. They both have 33k on them, but the MS6 is 3 yrs old and the MS3 is only 1 yr old. We'll see. I may still end up keeping the MSP if the payment isn't where I want it to be.
If you MSP is fully paid off, why not. I was thinking about changing my MSP into a year old MZ3 2.2CD but ended up with "nah, let's keep the MSP"