Want to setup basic home audio system

This may be the single most positive thread I've read on this forum since I became addicted to it ten months ago! 

  +1 panzrwagn
Regarding using Blu-tac for mounting stand mounts. That was my former go to for putting stand mount speakers on stands, brilliant stuff and helps stop ringing.

@diripio...Similar, yes. But in this case, more focused on 'distilling' uniform response from the speakers in your space.

The fact that it's nearly square can create 'issues'.  You don't note the ceiling height; assuming it's the 'typ. 8' h.' makes it easy to 'overdrive' the space.
You might as well sit inside the woofer's enclosure....I'm not surprised the Marshall 'rules the room', even at low levels...
They do that.... ;)
Better to concentrate on uniform response at lower levels; you'll be surprised at the details that easily get 'blown away' and missed.

Some room treatment ought to be in your future.  Refer to the forums and the websites that deal with that, and listen carefully to the room as you proceed.
Some here will claim that the space is half the equation.
In a small room...they're right, but best approached with patience.

You will have to listen like you've never attempted before.
Don't stress over it....this is supposed to be fun, after all.  ;)

Have @ it, J

bob540: 
I see a lot of people selling kef q50’s and q80’s near me. Sadly, no q550’s though. I have seen the ls50’s recommended a lot on reddit. Maybe I should call one of the listing just to hear kef speakers. 
panzrwagn & rixthetrick:
wont forget to pick up some blue-tac! Good call!

asvjerry:
The details are what I want! I believe someone posted on this thread a website that sells room treatment panels. That is definitely something I will look into when I get the chance! You don’t suppose they sell the mic used??

Diripio, congrats on the NAK purchase. let us know what you think of the speakers you demo.

Re panels, you can easily make your own. Check out ATS Acoustics online.They make them and sell supplies for DIY.  I purchased the Roxul Rockboard and burlap fabric from them  (might find the roxul and fabric locally) and made frames from 1x3" pine.  

Placing panels behind speakers, at reflection points on right and left wall, and behind listening position works well for me. My room is 12.5' by 14.5'. May need bass traps in a couple corners as well.  
The amount and nature of room treatment is, like speakers, a matter of room interaction and personal preference.