Okay I Bought the Magnepan 3.6's

Okay, I actually purchased the Magnepan 3.6's; now it's amp research time! Temporarily running them with my 22 year old NAD 2200PE (don't laugh, it still works!)...and they sound decent in my 17 x 26 room. However as it has been said before, 'Scotty, I need MORE POWER!'...

After some feedback on the Parasound and big Macs, I have been leaning more towards one of the Pass Labs. (Good deals abound on used ones)... So, which way to go? These look very promising:

X250.5
X350.5
or even the XA60.5 (Pricey!!!)...

Thoughts and recommendations? Also, safe to run a tube preamp in front of these?