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

I'm reaching the point soon where I'll invest in some treatments for my two channel listening room. Standmount speakers with tube amps. Room about 28x14ft with low ceilings, 6.5ft. Probably different kinds of treatments are needed. I'm not exactly sure yet what I'll need or how much to spend. This is not my final listening room, but I won't be able to configure another one for a few years.

I've seen many people tout GIK on this forum and I'm already communicating with them a bit. I will also reach out to Real Traps and possibly others. I do not feel bound to go with just one company or solution, so if you've mixed and matched, I'm curious about that, too.

Any recent comparisons between these two, or others? Do you have stories of good or not so good products or service? Any comments about the value of competing products? I'm not super handy or have a lot of free time, but DIY is also considered. 

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Lots of GIK purchases over 5 years, eg traps, panels, etc. Highly variable build quality ranging from no imperfections to corners not square, loose tacking of fabrics, and non-flat surfaces. Responsive and easy to work with customer service that always accepted returns. Their products make a strikingly audible improvement, but their quality control is disappointing (~25% construction failures). Good luck achieving your Audio Nirvana!
Also GIK will give you different advice depending which advisor you talk to. One will push you into going heavy with absorbing treatment, while another will recommend more diffusing. All that for the same room. At least it was my experience. Got conflicting opinions, granted it was a couple years apart. The first advice with more diffusion turned out best for my house of stereo system, but of course I bought the first set up from the second guy's advice lol. It is definitely a time consuming and error prone process. And with your low ceiling you need to be ready for a serious challenge.
Here is a really interesting video on DIY panels made from towels. The guy tests several different materials and cotton towels work the best. I haven't built any yet but I'm going to try it.

Just note that his test is technically incorrect. He is testing for sound blocking, not sound absorption though given the density of towels, I have to expect they would still work well especially at high frequencies. It's a cool hack.

"Honey, where are all the towels?"