About to invest in room treatments; GIK, RealTraps, DIY -- what is your experience?

I went through a very similar situation as you presently have.  Over the course of a couple of years, I read the books and literature, plus participated on Gearslutz acoustics threads.  That was most helpful.  It's good that you've done some REW sweeps; it was valuable to be on Gearslutz in order to properly interpret the various sweeps and to know what they indicated in terms of treatment application.  

Perhaps I misread your approach, but it did not look like you started treatment with very low/low frequency treatment (which you should).  My room is about the same dimensions as your room, except for 9' ceilings.  I ended up treating the corners, floor to ceiling, with RealTraps Mega units, as GIK were not as effective as I needed.  All along  the rear wall (short wall), I use 10" Knauf  mounted in skeletal frames behind RealTraps diffuser panels which are sitting atop their  2' x 2' x 6" absorption panels.  This will give me pretty much what I need for LF control and diffusion.

I moved my speakers closer to the front/short wall to help speaker boundary/LF issues.   I'm testing the first reflection/side wall areas with near diffusers and with combination of diffusion and absorption/range limiting to preserve source content.  On the front/short wall, in addition to the 34" wide corner Mega traps, some additional very effective absorption is necessary; I think you'll find the same.  

Ceiling area just above and toward the front of listening position is something you can determine with additional sweeps and experimentation.

The reason I used RealTraps corner units in addition to their effectiveness and quality build, is that I just did not want to build those myself; predictive software models weren't what I would want to use to build, etc.  However, for non-corners, regular rectangular absorption panels are a piece of cake to build, and pretty cheap.  Knauf from Home Depot comes in pieces that fit just right, at less than 20 bucks a panel, and in thicknesses of like 6" (minimum you should even consider) to over 12".  Knauf has tested very, very well.  A simple skeletal frame is cheap and easy.  You'll save yourself around $1,000 or more for the amount of absorption you will need in your room.  In order to afford the RealTraps units, I had to save money elsewhere.  That said, a few GIK 6" with range limiters was also something I figured in my scheme.  

I suggest you consider calling Ethan Winer at RealTraps for advice.  You can take it or leave it at the end of the day.  He is very nice and quite patient.

Take your time.  Address one issue at a time.  Keep running/interpreting room sweeps/measurements, then move to the next issue as indicated.  Be careful of over absorption or using where not called for.  Move your listening position and speaker distance from front wall as necessary.  

I've used GIK Acoustics twice for two different homes over the last 12 years.  Good advice/service, highly effective products at very reasonable prices.  Their business is booming right now, so you may have to wait 8 weeks, like I did, to take delivery.

GIK requires full payment on standard production items, while making you wait 8-10 weeks....even for a several thousand dollar order!  The actual production of the product takes about 2 days.  No partial deposit allowed.  Of course, GIK has required full payment up front for years, but the wait used to be about 2-3 weeks.  You'd think with a $54M annual revenue and exceptionally long wait times, they'd modify this policy.  

OTH, RealTraps makes a better product with a three-week wait, so there are choices available.  

Finally, don't use dense/rigid foam products for early reflections/side wall applications; they do not perform well for that application.  Instead, choose a medium weight, medium density, minimum 6" product such as Knauf Ecobatt.

@nolojunko is correct regarding the long lead-times and paying up front with GIK, however, from a value standpoint, GIK's products sell for roughly half the price that RealTraps do... so not necessarily an apples to apples comparison.   I've heard nothing but good things about RealTraps products... I just didn't want to pay more (2x) when I know from past experience that GIK's products are effective and a better value for me.

@audio2design
I have had a mic and REW for 7 months and have done hundreds of measurements. I thought I mentioned that, but I agree with you that this is an absolutely necessary prerequisite to spending money on the room.

@pdreher Thanks for the head's up about wait times for GIK. Will probably try to confirm about wait times. Others have suggested others, here, too, such as ATS Acoustics. That may be a good solution, too

@rbstehno  good rec's. thanks.

@midareff1 thanks for your experience report. nice room!

@martinb Glad to hear of good experiences with GIK. I will send them a scan, I'm sure.

@hornps Good to hear from someone with a similar ceiling height. Dennis Foley said to me, "Worst ceiling height I've ever encountered in 20 years. Find another room." Good to hear about GIK.

@nagel Good to hear your story, too. Thank you.

@nolojunko I have not started treatment at all. I have been doing analysis for 6 months (learning) especially focused on 20hz-300hz only, because bass is most important to figure out, first. I've optimized LP and Speakers. Working on scans with sub(s).
I've heard good reports about RealTraps, too, and they're on my list.
I had not heard of Knauf; not against simple building project, and agree about complicated corner traps -- too much for my schedule/abilities. I suppose you're not warning against OC 703 in your comment about "dense/rigid foam" or are you? Now sure what they're best called.