[Crion]

This would be the suggested 7.0 speakerlayout:
DSP6000 24/96 fronts
DSP5500HC 24/96 horizontal center
DSP5000 24/96 side speakers
DSP5000 24/96 surround speakers

All speakers run as large, skip the sub for now, all speakers will put out LFE in the room. The only thing you need to verify is that they are 24/96. The only important thing about them.

Processor + music server and 2x 3,5" HDD Storage:
861v4 + MS600 Source + MD600 Storage
or
861v6 + ID40 Music Zone card + MD600 Storage + 7xRevivers (150Euro/converter to convert each speaker to Speakerlink capability)

HDMI video switcher, upsampler:
HD621

As for compromise in regards to 2ch Watt Puppies, I don't believe you have one. You have more effortless sound here, more power from the DSP6000 while extension is smooth, also if you like Trifield for 2ch music your horizontal center will pick up the center soundstage and you will have a more even wall of sound even though your fronts are spaced further apart because of the screen.

PS. For center, select the DSP5500HC or better, do not pick DSP5kHC/DSP5.2kHC. DS.