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

It still boils down to treating that room for that issue. There is no getting away from the 8, 9, or 10 foot problems unless you're a horn guy (which kind of helps) and room treatment. Above 12 feet, lower the ceiling. Open floor plans get some roller panels and or heavy floor to ceiling acoustic theater curtains. You can open or close to dampen more or less.

Regards

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!