Surround Amp How's the Layout Work ?

I new surround user .
I had the lid off my unit being curious and all
My unit has or looks like 8 output transitors or power chips . I find this kind of odd seeing the amp has 5 channels in it .
Are the amps in the units one big amp and the power out put processed an sent out to the channels ?

I was exspecting to see 5 amps one per channel with the coding \decoding before going to the output section .

Most stereo amps have like 2 channels with an amp per channel
better amps have indivual amps and some times there own trans foremrs as well.
.
I just like to know the workings of these amps for the future if I want to get a better uni t and what to look for in the amps setup if one design is better than an other .
thanks