Very large room HT

Regardless of room size, IMO both 7.1 and matrixed 5.1 to 7.1 media is far more entertaining than 5.1. Use matched speakers, no dipoles.

If this is a dedicated HT system I suggest going conservitave except for the display and the sub/s.

7.1 does not say anything about the quality of speakers, amps etc. Wenn you use an amp which give a 2-dimensional image ( most do) you never will go higher than standard audio. Also wenn I play in Multi channel the stage is superior to all the 2-dimensional brands. I play 4-5 metre behind the speakers. And 1 metre beside the speakers. Bluray music is stunning because every instrument plays full touchable and to point out. Often instruments play far beside the speakers. For many it is a new experience. It is that convincing that people understand the new level in sound.

Thanks for your advice!
I realize that I need a good multi Chanel amplifier,
And preamp,to drive a 5.1 set of B&W with 804 as rt and lt?

First choose your personal speakers. And please do not forget B&kW make fine speakers but they lack a deep and wide stage. This is the most exiting part in highend audio. I did not go for the B&W 800D. I wanted to go to the next level for the absolute sound. B&W could not help me anymore because the stage was not that wide and deep. A 3-dimensional sound is wenn you see the biggest smiles on people there faces. I hope to give demo's in the US as well. Because I want people to hear how much more thrilling 3-dimensional sound is over 2-dimensional sound. Many people came to me during the show that they did understand what I meant with 3-dimensional sound after hearing the demo. It was new for many, even for shop owners. For me it is normal. I started in music and audio wenn I was 6. I got a big Philips stereo tube recorder.

Dear Bo
Can you detail your system?