Coming out of the blackhole called work...retirement

Amg56,
Congratulations on your retirement.
You have received some very good advice from various posters.
I am in agreement with mitch2  in that you need to decide what type of sound and system you want. Definitely you need to get out and get exposure and attending an Audio show is an excellent ideal.

As mitch2  said you need to hear all varieties amplifiers (tube,transistor, class D, low power and high power). There are many choices available in terms of speakers (and there are many!). In fact each category of audio component will offer an enormous number of choices.

Get the needed exposure to High End Audio products. Since you re Building a new home seek expert consultation regarding the listening room, this is of paramount value for you. You have a very generous budget and can construct a superb system at that level. In my opinion you can spend less and still develop a superb sounding system.

The key point is get out and listen to all manner of audio equipment and develop a sense of what you want your system to sound like.
Charles

amg56: Congrats on retirement! Question: Are you married? If so, how does the Missus feel about loud music playing while she is trying to watch Dr. Phil? Maybe you should consider really good headphones? P.S. Where will you reside? What kind of music do you listen to? Makes a difference in kind of speakers you'll need.

Since you re Building a new home seek expert consultation regarding the listening room, this is of paramount value for you.

In particular, you might reconsider the 5m x 5m dimension. A square room generally invites the most standing waves. Find some odd dimensions or get all Golden Ratio for example.

It would also be worth your time (and fun!) to spend a weekend at an audio show.  Unless you are in a major city with good brick-and-mortar options, this is the only way to hear a lot of things and find a frame of reference for the kinds of gear you like and don't.  Unless you're spending a half-million dollars, your system will involve compromise; hearing a number of rigs is the only way to understand which compromises you are happiest to live with.

Congrats on your retirement.  Retirement is not as good as people say... it is much better than that.  You have a great opportunity here to put together a very satisfying system.  As others have said; a combination of audio show attendance and visiting audio salons with some of your favorite recordings in hand should help you begin to discover what direction to go in crafting a system.

As others have said, it is not about the money invested but rather the care in assembling components that play nicely together!  In the end, the system has to satisfy you. Go with what sounds like "music" to you.

Enjoy the journey!