HT seating dilemma

other dimmensions are required for any real recommendations here. Also, is the room adequately ventilated with AC? If not, expect a hot room!!!-which no one likes to sit in. Trust me.

Ah yes, build a riser, and 14 feet from the screen.
How big a screen? How good of resolution? HD? HD anamorphic viewing? All this will make a huge difference in pic quality and viewing experience. So I'm just curious.
Also, and as important (to me, anyway)is "WHERE" you are planning on putting the riser? What dimmensions are the seating going to be at? Balance is key here.
Also, is the room closed off, and a dedicated space? Or is it open to other rooms, with odd dimmensions, as opposed to rectangular/symetrical? If the later, It all GREATLY DEPENDS on, yes the whole screen setup/persective, etc, as well as where you plan on putting the speakers!
For instance, if you plan on inwall/onwall speakers, you'll need an EQ in the system (or dsp room correction), and seating possitions should be at one particular dimmension in the room. If you go with speaker that are out in the room more, depending, you would consider other seating options, in my experience. So it all depends. What are you planning in the equipment/speaker setup? Have you thought it through?
For instance, I went to an AVS forum "home theater meet" at a members home a couple of years back (his theater was featured in a home/theater lifestyles magazine recently, of some sort, but forgot which one) and this theater was for a bit larger dedicated space, where the seating was 3wide x 3 deep, and "mis-setup" if you ask me. Yes, in the front row, he had a center "the so called sweat spot" chair, which was placed in one of the worst acoustics spots in the room! Although in theory, it was anchored between the speakers up front, but acoustically flawed from the start. There were other issues with his setup, like poorly placed speakers all around, and mis-calibration, even lack of acoustical treatment. But that's another story.
The problem with a set up with a center seat, placed equa-distant between the walls and main speakers, is that the huge peaks and dips in the response, make a high fidelity, even accurate sonic experience IMPOSSIBLE!!! Basically, you'll always be sitting in nulls, or "holes" in the response curve, that you can never fix! (the peaks you can nock down, with trade-offs for off axis seating, often).
So, I gotta know more about your room layout.
If it's not symetrical, there's options, and you can do more of a "sweet spot" setup, with one center seat. Otherwise, in a symetrical room, for mostly ht dubties, and multi-seat music listening, I'd personally forgo a center, and do seats at "odd multiple ratios" with the side walls, meaning two and/or 4 seats, side-by-side, with options. Basically, "no center seat". That way you'll be able to achieve more accurate response from the system, and better overall sound.
It's a trade-off. So you gotta know your trade-offs.
So, what's the shape and layout of your room?
I'd also recommend, likely against having your back row (if you end up with one) up against the back wall, as it will be
boomy back there, with other acoustical issues to deal with, and you'll need more EQ'ing of the system, with likely compromises in the back seating.
So, what's your layout like? And the speaker options?

As for the heat in the room, may I strongly encourage you put the equipement OUTSIDE of the room, preferably mounted in a closet, maybe protruding from the outside wall, inside a closet, etc! This will serve to not only help keep the heat out, but will eliminate the distracting lights from the equipment, and clean up the look of the room (unless you like the look of little lights peaking at you in the room, as part of a look/feel), and will issolate sound from the equipment, and sound from the equipement from the room. It's a suggestion.

"Will have my 2 ch speakers out into the room a few feet. i basically want something like this...
forum.audiogon.com/cgi-bin/fr
Looks like i will bring in a chair to put in front of ht seating for 2 ch listening." (streetdaddy)

Street? Notice that the room in the link you provided, as an "inlet" on the right side of the room, across from the front seating area. That relief area actually creats a change in the acoustics in the room, and changes the modal pattern, which makes a "dedicated center seat" a more flexible option than in your symetrical closed in room! In the scenario I think you're describing (perfect rectangle, closed-in), you ALWAYS be sitting in a null at 40hz, 121hz, 202hz, and 283hz
reigions! Basically there's going to either be a hole at those frequencies (in which case you'll hear very little, to no response there at all), or serios dips to contend with, likely!(uneveness with the rest of the spectrum. This is not a ideal funamental scenario for high fidelity, as a foundation.
All I'm saying is consider your "center seat" or sweet spot setup, as you're dealing with limitations, and thus some compromises are inevitable. So, what's your priority?
You can do the two channel room in another room, for a single seating setup you know. It's a thought.
As for rows of seating, you could get away with 3 rows back, if you had the right pj ad sources for hd. But it depends.
two rows, might be all you want/need. But, again, consider your issues to deal with. Also, the lifestyle for seating, company, etc.

" I was planning on sitting 38% from the rear wall as instructed by Ethan Winer of Realtraps fame"

Someone telling you they think 38% as a ratio for you to chose I think is rather blanketed and "uninformed" personally! It all comes down to measured response, and uniformity across the seating areas (or at least main seating area). You may very well put a row, or so, of seats at 38% from the back wall, and such--but what does the overall measurement of the response curve measure from there?! Reasons why a blanketed number like that will never work (unless you get lucky as heck), is that all rooms are different, and all speakers are different! This means the actual combinations of variables will ultimately determin.
You really need to measure and listen from different locations to pinpoint the best seating locations. All the guessing and "blanketed formulas" and ratios in the world won't mean anything if they don't actually yeild good sonic foundations!! Basically, you gotta go through the steps. Otherwise, TAKE A WILD GUESS, stick some seats where YOU THINK they might go (that goes for the speaker possitions as well, AND HOPE FOR THE BEST!!! Well guess what? It most never works out as well as you hoped! Like you said, there's a lot of issues to adress, and variables to consider.
Basically, sounds like you'll have one center seat for you to do "stereo" music listening, so that will be a "compromise seat", so you can get your "imaging". But be warned, you'll have the issues I mentioned there.
Personally, if I were you, and I had some budget to play around with, I'd STRONGLY CONSIDER contracting someone like Rives Audio to at least plan out your seating, speaker placments, and acoustic treatments for you room, and take a measurement or two-at THE VERY VERY LEAST! This couple thousand investment will yeild you better results than 10's of thousands spent on even the best gear money could buy! This is no understatement. Otherwise, some other competent acoustical engineering company. It's a thought.
Basically, the truth is, you'll get down to GUESSING where everything goes, and not knowing anything about what's doing what in your system. Otherwise, consider lots and lots of reading, and trying things for your self.
good luck