Jeff Rowland to what?

You have put together an incredible system that surely must be satisfying and enjoyable.  I am certain that you are fully aware that your Monitor Audio PL500 II's are a 4 ohm system.  My only suggestion would be to contact the speaker distributor representative directly to discuss the particular amplifiers that they use with that speaker. Many times they are reluctant to divulge that information fearing the information would be an endorsement.  
Guido may have answered your quest!
Often there are is a single amplifier/speaker combination that is simply magic.  Specifications rarely mean anything.  A 400 watt/channel amplifier by one company will not sound anything like a 400 watt/channel amplifier by another company.  Enjoy your Rowland equipment.  I for one purchased a different preamp after auditioning an Ayre.  They are not for everyone.

I’m keeping my Jeff Rowland components. I decided to tweak a few things and just enjoy what I’m blessed to have.

I'm a bit late to this game/thread, but thought I'd toss out a name that is seldom mentioned in the amp space: Linn.  I recently went from a Mac MC303 (3 channel 300W/ch) to a set of Linn Klimax Solos (driving B&W 802D2s and an HTM2 center).  Not only do the Solos run amazingly cool (I could cook steak for 6 on the Mac), but my 802Ds suddenly came alive in every respect.  The difference was immediate and astonishing -- clarity, soundstage, depth -- without so much as a burn-in period.  I actually started a thread some time ago wondering why no one ever mentions Linn Solos in a thread like this, and not surprisingly got two responses.  I haven't A/Bed them with other speakers (or against any other amps), so take it for what it's worth.  But I've also never seen a listening review of the Solos that was less than glowing.