Sound is better when I stand up?

@Samao

i had Ref 3A GV’s for years. Tosh Goka always advocated fine tuning of the front baffle with the adjustable feet. Can’t tell if you have stands that provide that ability. 

How close to the back wall do you have your speakers positioned.  I moved mine forward and it was a game changer.

Let’s review this:

you need the speakers custom tuned so that they sound brilliant when youre sitting down rather than standing up. Nothing to do with acoustics. Its the speaker crossovers need retuning

Notice the use of a chair without wings:

My first thought was, if you like what you hear when you're sitting comfortably, legs crossed, or stretched out or whatever you do with them, cigar impedimenta easily to hand, and a little of what you fancy in your best crystal within reach, then, relax, enjoy the music, and . . . STOP STANDING UP!

Facetiousness aside, I think the effect is mostly one of difference. You're more used to the sound you hear when you're sitting down and so there is a novelty attached to what you hear standing up. I 've noticed that if I stand and walk toward my speakers it feels as if I'm walking into the music. This is a nice way of experiencing the holographic effect of a system, but I'm a lazy b**** and much prefer sitting comfortably.