Jeff Rowland to what?

I have the Rowland M312 driving Avalon Indra's w/synergy lli pre amp. I have auditioned in my home the Pass XA100.5's, Bryston 7BSST and Arye MX-R monoblocks. They all are superb amps. There is something special with the M312/Indra combo. The Indra's need a lot of current and perhaps that is why I preferred them over the others. Also do like the fact they run cool and are energy efficient. The Pass amps were small heaters. lol.

I personally don't feel that you can improve on a new current-production JRDG amplifier for under $20K.  If you get a tube amp or a tube-hybrid amp you "might" get a result you like better, but for pure SS i don't see much real improvement in the way of refined sound or build quality.  
      If you want a significant improvement in most areas it's time for
a VERY good pair of speakers.  A 20x26 room (damped? undamped?)
is really quite a lot of space to deal with as well.
     I am a snob when it comes to evaluating listening material- classical music is SO much better recorded on average than anything else IMO
(acoustic folk and female vocals usually qualify as well). So,
IF your stereo system sounds good on Beethoven then count your blessings.  If your preference goes to pop music, "cool jazz", hard rock, etc. then fussy components like Rowland tend to sound a little "off".  In my book that's an acceptable trade-off.  

I've owned Wilson's, Aerial, Devore, Revel, and a couple more. Prior to purchasing the PL500 II's,  I listened to Rockport Aviors, Raidho, Dynaudio, and Magico S5s. To "my ears", the aforementioned speakers can't touch the PL500 II's. What speakers do you recommend I listen to?

I have been very satisfied with a pair of Herron Audio M1 amps.  I'm pretty much focused on sound rather than artistic cases or how much an amp costs and the Herron equipment never disappoints.  Without any consideration for cost, the Herron M1s would be on a very short list.

french fries has your frites

get better speakers (esp. if the ones you have now cost less than 10k)