Want to setup basic home audio system

@diripio....If that 'hard drive' is in your 'puter/laptop, there's a plethora of freeware of an audio bent....

My fave is  https://sourceforge.net/p/equalizerapo/wiki/Documentation/

...with...  https://sourceforge.net/projects/peace-equalizer-apo-extension/?source=typ_redirect   which makes APO a bit more 'user friendly', and allows to wring the best out of a speaker pair. *S*

And, after your feet get a bit more nimble....and a good calibrated microphone...
https://www.roomeqwizard.com/

The only requirement is running Windows, the faster the better.

Enjoy your Journey....J

@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