Room Ceiling Height for 2 channel listening - is taller always better?

16 and 17 are very nearly "square". Map it out, you will find the 16 ft modes are right beside the 17 ft modes. Sloping ceiling will distribute those, but focus higher frequencies. Everything you do has a different effect at different frequencies. 

One benefit of the high ceiling, the extra space can be used to hide as many and as large bass traps as you like. Mike did something like this in his room, only with side walls and cabinets that are angled to disguise the traps built in behind.

If I was doing mine again I would go hardwood, because rugs can be more easily moved around and changed. Carpeting wears and then one day you are looking at removing the whole system to replace the carpet.

Agree with Millercarbon. Hardwood is not only on my floors but also on my ceiling. Vinyl wrapped walls and insulated drywall. 

I built a new house with a custom room.  I used online calculator as a guide and did 18 wide 26 long 11 height. I talked to an acoustic company and they recommended 13’ ceiling or higher which I could not make work with the house design. I tapered the ceiling and 1 wall 6” to avoid parallel walls.  All corners are 2’ 45 degrees. The goal was to avoid standing waves and it did, the bass response is very even throughout the room. But lots of reverb/echo.  A hand slap takes almost a full second to die down.  My next project is proper treatments to tame the reverb without over damping.  To answer your question - yes go taller but you may want to talk to an acoustic expert before you hang the drywall. I wish I would have as it would of saved time and money and avoid another construction project. 

Room height must be balanced with length and width, but the golden ratio is not the way.

The science has been done at the School of Acoustics, University of Salford. They ran a hundred thousand simulations and found that most rooms are bad, a third are OK, and about 2% are good. The classic ratios were all bad, IIRC.

Rigidity is your friend. Otherwise the walls flex with the bass signal, out of phase, and highly distorted. I’m with Mike Lavigne on Quietrock 545, which I used. It’s more than an inch thick, 5 layers of drywall, and a layer of sheet steel. But it’s damned expensive. Plywood is a minimum. IMO

Good luck!

I worked for a large building materials manufacturer for years, we provided acoustic solutions and designed acoustic materials, acoustic room solutions, we had a testing lab and even an anechoic chamber.

Don’t get too hung up on the 2X4, 2X6, 2X whatever.... Only consider that if you are trying to keep sound from entering adjacent rooms. If that is what you are after, I would build a staggered stud (look it up) wall, maybe even use a resilient channel or "hat" channel to isolate the drywall from the studs, calk around everything and fill the cavitity with fiberglas. You don’t need to use anything expensive, just use a plain fiberglas. R-11 ill work fine.

Sound is controlled by absorbing it (insulation), blocking it (that is why people use drywall and double layers of drywall) reflect it, (room dimensions, hard surfaces, diffusers).

The key is using a combination of these to achieve the desired results. In a large room the sound will reverberate and you will get unwanted "noise" created from it. that is when you want to use absorptive materials like curtains, carpet or even absorptive panels. Thicker acoustic wall panels will absorb lower frequencies better than thinner panels (think low frequency - large sound wave needs thicker material to absorb it) so size and thickness are important, you don’t want to just buy panels and hang them randomly, you could do more harm than good. A large room is ok if you can control the sound in the room. People use bass traps and diffusers to make the sound react differently in the room. Hardwood with rugs is a good idea because you can move rugs around and try different areas, types.

Also... spray foam is not a good "insulator" of sound it is much denser than a typical fiberglas batt and could actually reflect sound more than absorb it. Use a combination of methods and play with varying types. It may take a while but you can get a good result. (minus testing the room for reverberation and calculating the amount, type thickness of material you need, that can get pretty expensive).