As for placement, I'm a fan of the Subwoofer Crawl for finding a few of the better performing locations in the room, say 2 or 3 spots, and then confirming with measurements. Even with Subs, an inch can make a serious difference in performance.
As to measurements, I'm more firmly in the Geddes camp and generally prefer strategic asymmetrical placement off the front wall. While I have not taken my placements to the next level by doing detailed analysis, I did get pretty good spots and am happy with the results.
As I build my new Subs over the next little bit and install them into my room, I will likely move on to that final step and get the Mic out.
Toward the latter comment, we will disagree.
Modern designs and modelling programs have largely taken the guess work out of designing a Subwoofer, and while maybe 20 years ago the concept of sloppy bass was still a thing, It is largely now just a stew of Audiophool Dogma and Marketing BS keeping that myth alive.
Obviously, if you buy Polk or Klipsch, you might not be getting the best, but in the ID world, the playing field is very level and major differences come down to personal taste and connectivity requirements.
That said, I haven't really ever heard a negative about REL other than their cost to performance ratio being skewed a little to much toward the former.
Of course, YMMV.
