NHT T-6 speaker placement

Sorry, those speakers are the NHT L5's

In your case I think I would go for the ceiling placement. Staircase location sounds like it might get kicked or damaged. Stair carpet will muffle the sound. Bar location will reflect sound causing imbalance in surround speakers. Bar occupants might be annoyed by surround speaker blasting over their conversation.

because of constraints with the structure itself, I ended up with placement just behind the listening couch on the sidewalls. It seems to work pretty well.

Thanks Bob, that was really helpful. The subwoofer paper was good too.

Basically, in speaker placement, everything is a BALANCE! There are trade-offs, compromises, and factors to consider, and it all needs to balance out for best performance. Or rather, it "should", if performance matters.
When it comes to rear speaker placement, as with mains and sub, I think it's wise to consider many factors. However, the main consideration for any speaker setup (in relation to the seating possitions) should be the fundamental "frequency response" from the speaker! This single issue alone, I find, is the single most neglected factor for most all, even from professional installers!!! It's sad but true. What happens, when response isn't considered, and poor speaker/seating locations are implemented, is frequency distortion, dynamic range restrictions, tonality shifts, "holes in the sound" between sub and speakers, balance issues in thesound,"boomy/peaky" unatural overall sound, obscuring of detail and vocals, imaging issues, etc, etc! High fidelity gets down to not only good fundamental equipment, but a balance of sound, tonaility, soundstaging, imaging, perspective, and dynamic range, including good acoustics and treatments, and it should all be considered if you care about sound.
So, for me, speaker placement must be first and for most be about oveverall SOUND QUALITY!!! Again, this is the most neglected factor usually.
Then considering proper stearing, envelopmenet, lack of distraction from the speaker (pulling you from the movie) from a "dominating speaker" blasting in your ear, soundstage cohession from seatting possition(s), etc.
As for placing speakers for proper stearing, soundstaging, and envelopment, there are going to be some preferences for each, but also some recommendations fundamentals.
For side speakers, you should try to go high for monopoles, and even a bit behind the main seating area. For dipoles, you should go dirrectly to the sides of the seating area, and you can go lower down the wall. For rear/back speakers, the same applies mostly, but I tend towards the middle/back of the wall for monopoles, or between seating possitions in an "even number seating arrangment", and dipoles dirrectly behind the heads, when using those! This also tends to yeild the the flattest response potential in the right seating arrangement, but it depends. (I consider all of this with mutiple seating arragnements, as opposed to "single seat" set-ups. Again, I consider the flat response when doing this, for solid fundamental performance and accurate sound fundamentals.
So, in short, things must be measured, balanced, weighed out, tested, tried, tweaked, even EQ'ed, and properly integrated with respect to all the other variables, seating and speaker possitions, crossover points, etc, etc.
This is why your average DIY'er has a very difficult time in achieving hi-fidelity, even superb, world class results from their investment!!! It takes years to learn what's all going on in a system.
I hope my suggestions help. Also, consider some of the newere processors with excellent "room correction" applications, and EQ circuits. These help greatly, especially once the fundamentals are adressed.
Good luck