Problem with integrated amps with R divide: 1) by having an extremely high output Z, the amp, the power amp is effectivly restricting voltage output as its necessary since most integrated are at least 30dB in gain. Now when your Zload >> Zoutput, you are making the load less sensitive to the input voltage and therefore you lose alot of the fine detail and you also loose control. If you look at damping factor (DF), you will see that in a R divide headamp, you have a very very tiny DF; and a tiny DF means lack of control, sloppy base, and loss of details.
Or I could just ask the simpler question. Why do my HD580s reveal lots of detail and exhibit great bass control when played through my Harmon Kardon integrated amp?
This goes back to the old problem I had when veteran head-fiers were trying to tell me that 580s couldn't possibly sound good through a battery-operated amp. I was sitting here reading that while listening to the 580s through a Headroom Airhead. And it sounded good. Great? No. But thin, lifeless, no dynamics, sloppy boomy bass? Nope. None of the above. And yes, I know what good audio sounds like. It created a bit of a credibility gap, as you can imagine.