Mine is less than optimal at the moment - I've always tried to keep speakers and power amps well away from the rest of the kit and managed quite well. The last 3 configurations were all quite successful:

1) Nottinghamshire - The main part of the room was 13' x 15' with the speakers a bit into the room in front of a big bay window, power amps right back into the bay. The room was, in fact L-shaped so it had a little 8' x 8' area off to the left hand side of the listening seat. The rest of the kit and all of the discs resided in there.
2) Lincolnshire - 13' x 24' room with speakers about 1.5 metres from the end wall (please excuse the heady mixture of metric and imperial here!). Power amps were on shelves built either side of the fireplace. The listening position was a sofa 1/3rd of the way from the back wall and the rest of the gear was on racks sat on the hearth on the inside of a blocked off fireplace on the back wall.
3) Lancashire - When we moved to this house, we originally put the kit into a little anteroom which is through a door to the side of the main room. The speakers and amps were at the end of the main room, which is sort of wedge shaped - about 18 x 16' at its widest and 18' x 13' at its narrowest. This was the best set up, though the speakers could have done with a little more elbow room. Then it transpired that there was a damp problem in the little room and a few of my record sleeves were damaged, including some of my precious first pressing FZ albums. Time for a rethink!

Nowadays, most of the kit is on two racks inside a massive stone fireplace, with one more rack off to the side of that (holding one TT, CD player and one power amp). The speakers are either side of the fireplace, but pulled well forward of it and they fire across the room rather than along it.

My own set up is speakers 1.5m away from the wall. This works well with my present speakers They are about 3m away from each other I would like to have more space and be sitting a little further back I have my speakers ever so slightly towed in It just my own listening preference with them My Hifi rack is behind the speakers

Ii'd forgotten that sitting near the back wall isn't normally a good thing. I think I've always been pretty close to the rear wall due to limited room sizes, I do like to have some item of furniture between the speakers with the exception of Naim IBLs. I also like the system right beside me although it always means running long speaker lengths.

As I switch between pre/power amps and integrated amps, I can't really sit a power amp between speakers too often. I've also had mixed results with long pre/power interconnects. So far only a Perreaux preamp with Krell and Brtston amps showed no loss of liveliness with long leads. All the others have shown some deterioration.

I'm only a couple of days from firing up a system in a new room, so it will be interesting to find out what differences I encounter. This one is pretty small, approx 14' X 12'6. Smal bay window which will sit in the mddle of the speakers. I still haven't decided where to site the electronics. Speakers will probably be a BT closer to ten rear wall but I will thankfully be able to set them further apart.

Celotex?

Foam insulation sheet; usually foil backed. Celotex is a brand name, as is Kingspan.

My speakers fire across the width of my 12x20 foot room. I always prefer that rather than firing down the length. Much better for imaging, imo, gives the speakers room to breath.

I have a GIK absorbent panel behind the listening chair which places my head less than a foot from the wall. That makes a surprising improvement and is pretty much the equivalent of sitting several feet from the back wall.

All other room treatment was removed with the arrival of my omni-directional MBL speakers - the panels etc just removed a substantial part of the magic.
Lots of reflective hifi kit, screen and pictures scattered willy-nilly ... the MBLs seem to thrive on it!

Here's a fairly recent photo.

I was told once by an acoustic engineer that the listener should sit in the more 'dead' end of a room and the speakers/performers in a more 'live' end. One room he treated, a converted double length garage, was a bit 'odd' at first, but the speakers being played, from HB1's to ATC 100A's, all sounded excellent, the HB1's taking on an ease and clarity I'd never heard from them before, hopefully because they weren't being smeared up by the room.