RMS is not a big deal...just a oil leak. Lots of cars have em. It is something that can get put off. IMS is another level of problem entirely.
I know of no Extended Warranty company that can reliably be depended to to be happily accepted by almost all mechanics, dealers and/or shops and which will pay an honest amount without fail for the major failures you might have. A CPO is the only one even close to that and you have to make sure you have no over-revs lest even that be questionable and limit yourself to dealer service.
More thoughts on extended warranties .