So what I'm after is 3D gaming sound positional accuracy and also sound quality. I do have the $$$ to spend on speakers (or more accurately, I found a really old but very decent 5.1 setup for very cheap - which I hope counts
), but what I don't know about are room acoustics and positioning/calibration. Do you know how I can go about setting these speakers up properly?
Well, if you have a lot to spend, why not get a 5.1 active speaker setup? Yes, you will have to tangle with cables, loudspeaker stands (for rear speakers) and powering all speakers, but you will get sound quality that will blow away most headphone setups.
Your price range is anything from c. $350/USD per loudspeaker (5 times that for 5 speakers + additional cost for the subwoofer) up to thousands per loudspeaker.
I would personally stay in uniform directionally loudspeaker designs with modern waveguides like Genelec, Focal, Neumann (ex-Klein&Hummel), Aurelia, etc. Most of them can be placed quite freely in near- to mid-field (not too far away from you as a listener), are not quite as bad in non-acoustically treated rooms as non-uniform directional speakers are, and usually have filters to compensate for bass & high frequency roll-off, so you can better fit them to your room acoustics.
Granted, this is more cumbersome and more costly alternative, but you the sound quality will be amazing, and the positional 3D accuracy par none.
If you want to stay in the sub $1000 USD range (roughly) you are probably better off buying a pre-configure 5.1 loudspeaker set (there are way too many to mention).
If you just want to spend say $300ish on the whole setup, then finding a used setup (proper loudspeakers, not a Logitech gaming setup) would probably be your best bett.