Rogue Audio also offers an upgrade of the Cronus to the Magnum for a very reasonable price of $650. Along with other sonic advantages, this would almost double output from 55 WPC to 90 WPC. It would be tough to get a comparable second external amp at this cost point.
http://www.rogueaudio.com/The_Magnum_Series.htm#GeneralFeatures
Best,
http://www.rogueaudio.com/The_Magnum_Series.htm#GeneralFeatures
Best,