Joa, wow does your dilemma ever sound familar! This is strange, I am sitting at Priest Lake on a wireless laptop chimming in to your question and I too am still trying to figure out what to do with my RX-1. It runs absolutely wonderful, has every mod but a turbo and I love it, but after riding the new sleds I'm just not sure what to do with the old girl.
You are certainly in the right camp now. There are many RX-1 owners now riding the new cats. We were all looking for Yamaha reliability in a lightweight sled and the cat motors just seem to have less issues than the other brands.
It really boils down to money. If you are selling your RX-1, I'd buy a 2010 M8 with a 155-160 hp stock. The 09 M8s were SO much better than earlier versions that it was worth it to me to buy an 09 vs. getting a killer deal on an earlier model and trying to reach the standard set by the 09s.
I find myself doing stuff on my new M8 that I had no idea I could do on my Rx-1. I now take much more technical lines, I can turn around and shoot back up a hill at the half way point, it seem slike my riding skills went up 10 times with the change.
I thought I wanted a M1000 until I rode one. The 09 M8 and M1000 Sno Pros I rode last winter were stock except for SLP pipes (and a fuel controller on the M1000). I was looking for a lightweight flickable boondocker too and the M8 felt much more nimble to me. I don't try to but, I always seem to make the M1000 guys mad when I say this, and Granted, the M1000 could have been set up much better but, the M8 surely could have been as well.
Since you aren't much into highmarking either, I think a 09 or 2010 M8 is where you should focus your efforts.
Good Luck buddy.
Frosty