My new room is 8 x 16 x 32, what to do?

Don't do anything until after you have setup your system and furnished the room. Empty rooms are notoriously deceiving about how they actually sound. It's only after you've experimented with how the room really sounds and how sensitive it and you are to changes in placement of equipment/listener can you start to devise a successful plan to correct any problems.

BTW, great sounding rooms don't have to conform to golden ratios.

FWIW most empty rooms with out domestic furnishings such as rugs, drapes, pictures, furniture, etc will have echo slap. Don't let that overly concern you.

Apart from room induced nodes in the bass created by room dimensions, most of your room problems can be controlled by two things; 1)deadening the first reflection points on floor, side walls, and ceilings (don't overlook the latter if you don't have WAF's), and 2) put acoustic materiels on the wall behind the listening position which diffuse/dispurse the mid/high frequencies I'd be concerned that if you have treated the first reflection points well that using deadening materiels might overdamp your room. You might also put similar materiels behind the speakers but I wouldn't do both and, unless I had panels or electrostats, I probably wouldn't do much to the wall behind the speaker if I did all the other stuff.

Bass nodes and nulls will be determined to a great extent by where you place your speakers and listening position. Trying to anticipate these issues in advance by determining exact room dimensions by a formula is an invitation to disaster, especially if you do it with out an expert on-site to help, and even then I've seen a few 'expert' disasters in special built and treated rooms.

IMHO, in a rectangular room there will always be some bass nulls and nodes and all you will accomplish by changing dimensions is to move them around frequency wise. If you have a gross node you can always use a parametric type equalizer of the digital or analog type or if the problem is in the upper bass you can probably get some good results from using bass traps etc.

Hope that helps a bit and gets you pointed in a good direction. I'm sure some of the experts will opine as well.

you are lucky to have such a large room.

you may be able to avoid some of the effects of room boundaries by placing your speakers away from the rear and side walls.

for example, you could move the speakers, say, 10 feet from the rear and at least two feet from the side walls.

i assume you will place a hardwood floor over the concrete and maybe a carpet over that.

i suppose you will also select appropriate materials to place on the brick.

what about windows ? how many and where are they. glass is a reflective surface.

i have 6 windows in my listening room. it is a challenging to mitigate the effects of all that glass.