Dynaudio Special 40

I am currently driving my Special 40 with an EL34 tube amp that is 35 WPC and it has plenty of volume for me for moderate listening levels. I cannot rock the house like I can when driving my Klipsch Heresys, but I don't typically need to play that loud. The 40's already have terrific bass, but I found that by using a sub I can get substantially more volume because I can set the high pass filter on my amp to match the crossover of the sub thus freeing up the amp from much of the low frequency work. It is really a great sounding combo.
 

Brother in law has these in 12’ x 20’ room w EL-34 powered VTL - really good sound, easy load - you should be fine IF you keep SPL reasonable 

I had the c20s for a little while. IME unless the Special 40s are substantially easier to drive then that Arcam would do them no justice at all.