It is always nice to hear someone say nice things about the gear you own and have been enjoying. We have alot of choices in this hobby and I have been fortunate enough to make some good ones with this kind of input from those who have been doing it for awhile. For me 601's + 500T + Alexia's = Its time to go listen.
I had my 601 meters bouncing at 600 watts yesterday on the S5's. Sounded incredibly clean.
Wow, 600 watts, I hope you have a huge room. I think the most power I ever used on mine was 60 watts, usually about 6 watts. I think I would be wearing ear protection with that amount of power and things would be falling of the shelves and walls.
For me That looks good as the MK1.2 or 2.