My system is as follows:
Front: M80
Center: 150
Surround: M40
Surround Banck:M40
Sub: SVS
B&K processor
Marantz M9000 for front, center and surround
2 Marantz M500 for surround back
Denon 2200 DVD Player

All speakers were set to Large
Last Sunday pop in the movie "Seabiscut", crank up the volume to -15db, I could almost feel the horses were running besides me. But all of sudden, the front and center lost the volume, initially I thought one of the speaker wire was shaken loose by the vibration. After thoroughly examined, all system set to go. I replayed the horse reacing scene again, same happened but when I lowered the volume and the sound came back. After reset all my speakers to small, I replayed the whole movie again without a hitch. Just want to confirm here with every pundit in this forum, the problem is my Amp, isn't it.

If it's my Amp problem, can anyone suggest a suitable one.

Wish I could help. I'm still looking at amps and have not come to any conclusions.

GS, if the problem occurs when you set the speakers to "large", but not when you set them to "small", my thought would be that there's a problem in the bass management circuitry of the B&K, not the amp.

I just look at MM9000 specs and I saw it's rated for 8Ohm speaker. The M80 you're using are 4 Ohms and the VP 150 is 6 Ohm. Possible that during the loud, bass heavy scenes the amp went into the overload protection. When you lowered the volume or redirected a part of the power to the sub by setting the speakers to "Small" it went back to normal.

As the non-expert, I find Gena's explanation a little more believable than John's.

Except that GS implies that the surrounds kept playing.

If the surrounds and surround backs kept playing then I agree with JohnK also. If the surrounds didn't play then I would tend to agree with Gena... however... are there amps out there that recover from protect mode if the system volume is reduced?

Sounds like some more tests are in order!

did any of your clipping lights come on.. i have the same amp as you, and have never had a problem, however i have 60's wich are not 4ohm speakers.

i would emagine that one of che channels would start clipping before it would turn the channel off, hence the whole reason for the clipping light indicators at the front of the amp.. the plastic "light" across the front of the amp are where the clipping indicators are located.