Apologies to Norah Jones, I needed more bass!

@erik_squires 

Interesting. Makes a big difference having enough power. I've been a big advocate of that for a very long time. I've never had the efficient low wattage gear so have always gone for big power.

The speakers that I've been using for the last 23 years or so, are quite power hungry and per the manual, are OK with up to 400 watts at 4 ohm X 4. I feed them with 385 x 4. The difference in going from one amp to two is enormous. I found them to be slow and flabby with only one amp and they did not come to life until I had them bi-amped. 

I'd love to hear the super efficient type sometime but I may never have that opportunity. 

@billpete  - In this particular case I tried to balance sensitivity and power.  With dual woofers in parallel I get 90 dB sensitivity (for 2 watts), and a maximum output around 110 dB/1m with a little wattage left over. 

@erik_squires So, to do that, you need an active crossover? 

@billpete - Not sure what part you are referring to, but if  you ask, did I use an active crossover to triamp?  Kind of. :)  I actually use Hypex 2 and 3 way plate amplifiers which have built in DSP capabilities which includes filtering.  Specifically the FA123 and FA253.  

It does help that because I use no passive crossover I don’t have the usual power losses associated with them, either directly through resistor padding or indirectly through the losses of the frequency shaping filters. 

@billpete  - It may help you to see the wiring.  Take a look on my blog, the second picture shows how the amp is mounted on the back of the woofer section and how it connects to the mid and treble on the bookshelves. 

This saves me a great deal of device and wiring complexity.  I have 1 wire from the HT processor to the back of the plate amp, then short speaker cables to the top section.  This is a lot simpler than a "discrete" setup using a stereo crossover, plus 3 stereo amplifiers.  Talk about messy wiring!