Bridging amps, Good idea or bad idea?

It's true what Kurt's link says. Most amps when bridged cannot drive low impedance loads. Your owner's manual probably states what load you are limited to when bridging.

The damping factor is also cut in half.
More power, (on paper), and less bass.
I've tried it with Adcom & Parasound.
Both brands sounded better using just one channel of each amp.
That allowed the whole stereo amp transformer to supply one channel...
Try it in your setup.

The 840W is rated for 800W bridged into 4 ohms and the sub will help, particularly with an active xover. When you get close to the edge, even the wrong speaker cables can push it over. Depends on the speaker load... resistive, capacitive, impedance...

How about power? That's 2 X 2400W (at ear shattering levels), or 40A @ 120V.

Doubling and quadrupling isn't much of a absolute SPL increase but that's not what it's about. Closer to the point is whether that much power, without the low bass requirement, will benefit your speakers. I could understand for Maggies or Carver A3's.

The different times I tried it,I was disappointed with the results of the sound.Transparency,cleanliness,distortion, and changed frequency response just to name some of the drawbacks I encountered.

i was wondering the same thing myself . i had always heard that bridging was not a great idea but i have read that many users of the vac stereo amps that i am interested in trying : specifically the vac phi 300.1a and the vac phi 200 bridge them all the time . they apparently were designed to be bridged with a flip of a switch . i wondered if that makes these vac amps less than ideal when used in their monoblock mode . evidently the manufacturers don't believe there is any problem with bridging . still i wonder ...