Hi Stefan, hope you are well?
I agree that the generally accepted hi-fi view is to have 2 speakers in front of you, with the tweeters at ear height, about the same distance apart as they are away from you.
However, I've been doing some experiments to try to challenge this, and I would encourage you to do the same! I asked myself some time ago what effect I wanted to create from my speakers and I decided it was this:- I want the effect of a solo female vocalist (OK, I admit it, Marie Fredriksson from Roxette!) standing in my living room near the fireplace singing to me as I sit on the sofa. 
However, conventional stereo wisdom won't give me this, not convincingly. Hence, after many weekends of trial and error, numerous holes in the wall and (almost) a divorce, I settled on the following setup:-
Two RedLine 60 speakers mounted on the front wall of the living room, either side of the fireplace, at a height (measured at the middle where the tweeters are) of 165cm (5 feet 5), with the speakers pointing inwards to a point about 30cm in front of my listening position. The effect is simply AWESOME! I can now close my eyes and the second favourite lady in my life (just in case my wife reads this
) appears in the room in front of me........
This doesn't work for all types of music, but for solo vocals with beat-driven backing, it is the best setup I've ever found.
To address the issue of bass; yes, you do lose quite a bit of bass weight and extension by wall-mounting your speakers, however the RedLine's I chose (which I have extensively modified and upgraded, by the way) have way too much bass when on the floor. Lift them up and they start to sing! Depending on the room you are listening in, the 4000's can behave in a similar way. IMHO Beolab 6000's seem to be best on the floor in "free space", but again, this is room-dependant.
Anyone in the Leicestershire area who wants to come and have a listen to my system is welcome to do so; I do tend to get obsessed with my music but I think I've finally found a setup to rival the best, using fairly "low tech" equipment......
If I've learnt one thing from this, it would be:- ASK YOUR WIFE BEFORE YOU START WRECKING THE LIVING ROOM!
Steve.
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