Pioneer VSX908 Faults & Suggestions (please!)

Help!

My Pioneer VSX908 THX Receiver has developed some very worrying faults. The first problem showed up yesterday whilst playing a DVD with a DD 2.0 soundtrack, pro logic decoding sans THX. The sound came purely as stereo - from the rear speakers. Turning the amp off for a while and then back on again cured the problem, although I vowed to keep an eye on matters.

Tonight my girlfriend settled down to watch a disc, turned the amp on and immediately a regular loud "pulse" sound began to eminante from all five speakers + sub. Not wishing to trash my speaker coils I turned the amp off immediately. Zeroing the volume, turned it back on and switched to the CD analogue input - slowly turning the volume up, the same pulsing noise was still evident.

I'm concluding that the decoding processor itself is stuffed. Am I right in thinking this ?

For the record the speakers are M&K K Series, installed and callibrated last March by a THX engineer - I'm confident the speakers haven't caused the problem.

The amp has also had very heavy use, not only for watching lasers & DVDs but also for the integrated tuner. Likewise it has had more than adequate ventilation and is not obstructed in any way. the reciver is also over 2 years old since I bought it, and is no longer under any kind of warranty.

A few questions then, assuming my diagnosis is correct:

Is it worth going through an approved Pioneer service centre to have the receiver examined & fixed ? If it is the decoder chip, I'm figuring this could be expensive. Does any have any experience of using one ?

If it is likely to be expensive, are there any *reliable* online retailers dealing in mid to upper range THX certified kit ? (If you don't like the whole THX thing, fine and dandy but please don't troll me on it!

Finally does any one have either the Pioneer VSX-2011 receiver or the Denon AVC-A11SR care to offer an opinion on either of these ?

Any advice greatfully received - I'm desperate!

Cheers,

Brendon