[mgsboedmisodpc2]

The headroom of my system has increased somewhat after adding the 2QW because the Prima Luna 5 does not have to deal with a frequency spectrum it has a problem with bass.  So prior to the addition of the 2QW the fuzzing sound coming thru the mid range of these speakers during sustained low bass notes from organ music I no longer hear with the addition of these subs at my normal listening level.  I guess if I turned the volume up the fuzzing sound thru the mid range would return.  So are high powered amps necessary when paring these speakers with a sub?

[Carl V]

isn't your amp. a KT88 based amp?
What speakers are you running?
How Loud? (at the seat?)

There maybe something else amiss?

many moons ago in grad school
I bought a PV5 , MV50 2Ci...then added a 2W.
Sounded good.  Added a second MV50...got better.
vertical passive bi-amp. The added the second 2w.
Then MV52 upgrades. PV-5 tuned up & tweeked.
that system is still charming my uncle. latest sig upgrade.

[mgsboedmisodpc2]

"isn't your amp. a KT88 based amp?" yes currently running KT120
"What speakers are you running?" Vandy 3 not 3a not 3aSIG
"How Loud? (at the seat?)" good questioin
Well the MV50 has 45 watts and the Prima Luna 5 has 32watts neither of which can drive the model 3 very, very loudly 
when the music has lots of low frequency content

[mgsboedmisodpc2]

One reason why my Prima Luna Prologue 5 amp with KT120 tubes sound better thru my Model 3(s) when using the 2WQ subwoofer is because of less voltage demands placed on the amp when using the X-2.

From TAS 206 review of the Model 7
 
"Among the benefits of a powered woofer are less strain on your main power amplifier (it needn’t deliver current through the woofer), the removal of the series inductor between the amplifier and the woofer (a huge benefit, by the way), and a more benign load for your amplifier (the speaker’s impedance is less reactive)."

[Hear Clifford Brown]

Your question was "are high powered amps necessary when paring these speakers with a sub?"

Based on my experience the answer is no, you can use 2Wqs with low powered tube amps.  I did with excellent results.  I have two 2Wqs and used them with Coincident main speakers that are fairly high efficiency.  The amps in that setup were 300B mono blocks about 8 watts, a Decware Rachel amp with 6 watts, and a Tube Audio Lab 45 based amp with 2 or 3 watts.  Having the subs made it possible to use the 45 tube amp.