Hafler DH-220 monoblock vs stereo


I have a pair of Acoustat 1+1s and an RH Labs sub that I'm driving with a pair of Hafler DH-220s that each have the DH-202 Bridge Kit installed. (Yes, it's all *old* but it still sounds pretty good!) The other evening, I was chasing a gremlin and decided to swing the cables and switch one of the amps to stereo. I was astounded by the change in the sound. It was MUCH more detailed and "present" vs using both amps in monoblock mode. I figure I've gone from 350wpc or so down to the 120wpc of the single stereo DH-220 amp.

Why would there be such a change? And a rather postive one at that? 

The "downside" now is I'm thinking that if it sounds this good with only 120wpc, maybe I should start looking for that tube amp I've always wanted! BTW my pre is an ARC SP8-II.
Thanks!
edwardjguzman
Post removed 
The Accoustat 1 + 1's have an impedance of 4 ohms at low and mid frequencies, falling to <1 ohm at high frequencies. A bridged amp will see a resistance of HALF of these impedances. Therefore DO NOT use a bridged amp with any speaker whose impedance falls below 8 ohms. Too much current draw from the bridged amp. If you want to hear an improvement in sound quality try using a single channel of each unbridged Hafler into a single speaker. 
Tube amps are a BAD choice for driving electrostatic speakers where the impedance at high frequencies is 1 ohm or less! Also a non-flat impedance curve from low to high frequencies makes them subject to Ohm's Law. Tube amps in general have output impedances of >1 ohm. So they will have a non-linear response into any speaker without a flat impedance.
I have a Hafler 220 in my collection. It is an excellent and fine sounding amp! No need to replace it!
@roberjerman2: Your statement about not using bridged amps with my setup is an interesting one. You see, I've been using this setup for well nigh on 30 years with no ill results. No blown amps. No blown speakers, etc.
Your suggestion about using a single channel from each amplifier is also intrigueing. There's no increase in power over using one amp for both channels. What are you thinking I would gain by that configuration?
Thanks,
E.