I'd say get at least 1m of space between the listening position (LP) and the wall behind you at almost any cost. This for reasons of bass, mid, top, everything. I have a narrow room, and here I found it better to fire down the room and put the speakers near to the side walls and treat the side wall first reflection points. (I recommend diffraction - note this is not diffusion and it's not absorption - like this sort of thing
http://www.jocaviacousticpanels.com/uk/products/dif.dynamicflow/index.htm. I actually have DIY versions made from white guttering ... how I arrived at this is a topic for another thread! But if your room is big enough to stay away from side walls, ATC recommend 1m, all power to you.)
Starting the LP at 1m from the wall behind your head, if you find the bass boomy (room mode) then move the listening position forward until you find you a spot where the room mode isn't too bothersome.
If by the time you find the above point, you find the overall sound is too bright, you can move the speakers nearer and nearer against the wall behind them to add warmth.
I found a tension between the two goals (LP into the room enough to tame the room mode vs overall sound warm enough). If you can't find an acceptable compromise, this is where I found tuned bass treatments at the room mode frequency mitigated my room mode, allowing me to move the LP back a bit more before the mode got bothersome (but, I urge never less than 1m from the wall). Tuning frequency of the traps must be done accurately with measurements (I use XTZ Analyzer).
An equilateral triangle between speakers and LP is a decent aim, "ish".
Bit of a dark art because every room is different, there are some strangely-shaped rooms for example.