For a two-channel sound system I suggest that you consider the Audio Research LS-17 preamp with a Musical Fidelity M6PRX power amplifier. They will run about $7500 total and give you sound to die for.

I use the Vandersteen Treo speakers, which run $6000 per pair and are IMO the best you can get for under $10K. I recommend them highly. Vandersteen has made a huge number of high-end speakers over the last 30+ years, yet you almost NEVER see used ones for sale. That will tell you something about owner satsifaction. Once we get them we don't want anything else...lol. I have used Vandersteens in my main large system for nearly 30 years.

My second choice, if i did not have Vandersteens available, would be Focal speakers or Vienna Acoustics.

For a subwoofer i use the NHT B12D subwoofer, which runs around $800 each. You will want two of them for a large room. Highly recommended.

If you are going to have 5 channels, then I suggest that you get the Cambridge Audio 751R AVR. It is the best-sounding multi-channel receiver in the world IMO. It has more than enough power to run almost any speakers in existence without additional amplifiers. It runs less than $4000.