No headroom andclipping might be why the B & K 5000 sounds better.
a question about the behringer, it says that its "2,400 Watts into 4 Ohms bridged operation", will not that destroy my speakers?
also from HK's 75 watts to emotiva's 200 watts will i notice a difference that i will really like, or will i be able to say 2 myself that's money well spent?
thanks again, sorry to the OP.
On more response and sorry for hijacking OP but it also answers an OP concern about headroom and is the only posible explanation I can come up with for his improved sound.
If you are currently running your AVR as loud as it will go all or most of the time, you could be possibly clipping your signal which is very bad. It is also considered no-head room to be running at or close to max because if a stronger than normal frequency signal comes in that will clip and imapct the overall sound quality. If OPs current setup is running at max and the B & K 5000 adds even a little increase it might be enough to make it sound better. If your HK at 75 watts is maxed out you might see an improvement, otherwise you won't really see any. However the main HT component that affects sound are the speakers. The most improvement gain in in a system is to upgrade speakers.
Now concerning the 4 ohms bridged into a mono channel, meaning you connect in series the 1200+1200 into 2 ohms + 2ohms for a single channel; you are not going to run like that. also the pre-out input can be varied and that change also changes the amplifier output; you do not always run at maximum.
The Behringer shows a spec of 1200 watts per channel into 2 ohms. A rule of thumb is that when you cut the ohms in half you require twice as much power ( there is some loss due to inefficiencies) so 1200 watts into 2 ohms approximately equals 600 watts into 4 ohms approximately equals 300 watts into 8 ohms. Even at 300 watts you will not be running ( or should not be) the pre-out at maximum into the amp.
One other consideration is how sensitive or efficient your speakers are. Less efficient speakers (and some high end speakers are 4 ohms and inefficient and require lots of power; external amp almost always required) require more power than high efficient speakers. Speaker efficiency is meseure in dBs , low sensitivity (80 db), average sensitivity ( 88-90db), high efficiency ( approaching 100 dB). Also, remember the speaker impedance varies with frequency so it is not constant and a nomina; impedance is usually specificied. 4 ohms requires twice as much power as 8 ohm and 6 ohm requires 1.33 times as much power as 8 ohms.
Peace and Good luck to All
Forest Man