Very large room HT

Here's how all this works..
First, Vast majority of consumers systems, regardless of expenditure, have chity performing systems, that are no where near the capability of what they COULD have ended up with if they did it right in the first place! Truely, Home theater in a box, Bose, and similar would have done them just as good. ..cause they haven't a clue, and likelyl neither does their "professional" installer!
NO, THX is not just a certification! Can you get a great HT system that's NOT THX? Sure! Problem is 99% of all audio enthusiests and consumers alike don't know what they're actually doing, and the acoustics are already likely a huge obstacle to great performance to begin with! Thus THX is an easier integration, comparatively, that has a much better fundamental chance, all room setups acoustical challenges, and likely issues that will come into play during setup aside, if it's not broken, don't fix it!
Worked in 6 high end audio video stores over the past 2 decades, and sold/did it all. ..Did all the custom, was an avid audio/vidoephile, went to CES EVERY year, including "The Show", Cedia maybe once (custom is a bit dry and boring..so I sourced it out when I sold systems), read about every document I could find on room acoustics, and played, installed, and built most every type you can imagine, and implemented them. Oh, and along the way, tinkered with modified AV gear, custom loud speaker implementations, took classes for calibration, theory, integration, acoustics, yada yada.
So here some of you people are... giving other people advice to simply go down and listen to find out what you like! YEEEAH! As if this was going to be an indicator as to how that same equipment that they heard, in some other room that's TOTALLY different than their own- btw, was going to perform after THEY set it all up in their own home setting!! WWWROOONG!
This is why you can't simply read a magazine recommended review, list, or someone's biased opinion (as a zealous green-horn audio enthusiast, who just got his first job around gear working for Best Buy /Magnolia, and still doesn't know what they're talking about, no matter how excited they are about all this stuff they think they know!)
NO ..you can't go to CES, and listen to a "Monitor Audio" ht setup, and expect that the industry is suddenly going to stand up with high praise and accolades, showting "THIS IS IT! ..THIS IS THE SINGLE BEST HOME THEATER EXPERIENCE WE'VE ALL BEEN SEARCHING FOR!!! AAAAA AAAAA AAHHHAAAAAAA!!!!
No it's not going to happen, and those same speakers you might have just liked with some pop music playing suddently don't sound so good in your 8 foot ceiling, poor acoustically laid out living room, vs what you just heard in a large high ceiling carefully laid out and acoustically friendly arrangement, which you heard at some esoteric high end audio salon, BEING DRIVEN BY $50K WORTH OF PREAMPS, AMPS , CABLES, POWER CONDITIONING, CD TRANSPORT, ETC!!!!
It's all relative.
All I'm saying is that when I hear people getting on the bandwagon of some loud speaker design that they heard demo'd somewhere, and they suddenly get visions of the heavens opening up, and God coming down to bless your loudspeakers as the "end-all-be-all" of home theater nirvana, I JUST HAVE TO LAUGH! BBBAAAHAAHHAHAHAHAHA!!!
Yep, the reality is that people don't know, cause they really don't want to know!
Fall into the trap of simply going out and buying a pair of loudspeakers you listened to (NOT s complete system that's engineered for YOUR SPACE, in YOUR HOME, with YOUR SYSTEM), which you auditioned in some foreign audio shop, with variables you have no idea what you're dealing with, and you get what you deserve!!! All I'm sayin.
Bottom line, if you don't want to go some professional's advice, I recommend HIGHLY that those inquiring here, looking for a system to fit your needs (SYSTEM! - operative word here), simply go through all the av magazine reviewers, and look at what they're using for their dedicated HT systems! In fact, why not just email em and ask em what they use, and what they recommend/suggest you use as well?!!!
HEY! now there's a wise idea!!! Cause face it, otherwise you get every single enthusiests and 2 channel tube/analog audiophile who' uses nothing but a tube amp hooked directly to an OPPO DVD player as their "reference" AV system's, opinion on what's right for you!!
See it all for decades, and you can't reinvent the wheel!
Follow the experts, cause they are in the KNOW!
Probably the best advice I can give for someone putting together their own HT system as a project/hobby, who's trying to figure out the "pieces".
A wise man once said,"..the crowd is ALWAYS wrong!"

At the end the sound quality is what matters. This level says how good a system is. Many people said to me they did not understand what 3-dimensional means. But after hearing it became clear. Now it is very easy for them to understand. Why? because they heard it. Most of them never heard 2 and Multi channel this good. People came to me at the show and said; this is how it should be. Wenn they came in you directly hear the level in focus and in depth. It is that convincing. Even wenn you are not sitting in the middle, the focus is still awesome. You can spend your money only once. That is why I Always do different settings. For example: a source or amp of 2000 e with a pwercable of 100 e. And a source or amp of 1000 e with a powercable of 1000 e. The amount is the same. The end results are Always a lot different. Audyssey Pro solves a lot of acoustic problems. I had this year in a farm very good results with XT-32 in one of the most worst acoustics I ever had.

I think we should help the OP by keeping things simple...
maybe we can all agree on a few things and he will have to go from there....my experiences and opinions are somewhat different than yours and the next guy and so on...

1) at a price point of 20,000, we are way beyond the HT in a box.
2) speakers have classes just like cars do... you cannot FAIRLY compare a $1,000 speaker with a $5,000 speaker. and so on.
3) There IS a law of diminishing returns with home theater speakers and equipment. Is the OP going for a 90% awesome system or is he chasing after the last 10% of perfection?
4) even with room correctioncorrection... the best speakers/systems will not sound as good as a lower end system in a decent acusticly made room.
5) it seems that we are on the same page as far as saving the money and buying used
6) there are different ways to go about the idea of reproducing sound... electrostatic, ribbon tweeters, dome tweeters, and all the materials for them... people prefer different ones... it doesn't mean one is better than the other, just different.
7) it would be impossible for the OP to listen to all the speaker and amp and processor combinations in his listening room.. so he would still need to go and listen to speakers, even though they will be in acusticly different rooms.

if we can agree on these items at least the OP has a place to start.

Bill

Speakers are the way to start.

Ok friends lets start with speakers for 5.1 ,HT and possibly two very good front speakers for just stereo .
Than will get a really good amp and than I got to have a Pre with all the gadgetry,,,,how's that .
I listened to paradigm S8 and I gave it. 8out of ten !
B&W at best buy was to me 7out of ten
I am looking for the MA and the Revels
YOUR INPUT IS GREATLY APPRECIATED
SALMONI