Your sub experience: Easy or hard?

As Mr. Gross claims by slightly blending the subwoofers crossover region at a higher frequency to be beneficial in matching the main speakers lower frequency presentation. Simply by using my subwoofers Auto EQ feature followed by manually drag and dropping the subwoofers Frequency Response Parameters by ear. Easy.

Just as easy was determining the rooms ideal subwoofer positions which are, unlike Mr. Gross' claim of within (or near) the speaker, one of the worst locations in all of the rooms my system has occupied. 

I have been playing with various sub options, 1 sub, then 2 subs, then 1 large sub, RCA preamp in, High Pass speaker hook up, various manufacturers. I finally think I have found a good sounding set-up with 2 REL T5x-8" down firing subs using the high pass speaker hook-up, recently purchased. Very easy to set up using the instructions provided and some supplemental reading online.  I am in the process of negotiating for plant space with my Number 1, to move them around somewhat (always a bit of a compromise) and making some minor adjustments to volume and crossover. I am partial to more of a British sound, so more of low end fill, rather than "big", is what I have been chasing. After playing with apps and making continuous adjustments with other subs, these subs seem to be fast enough to not muddy up the midbase and blend in very nicely. I was almost ready to through in the towel on subs and start looking for a three way speaker system again.

I have tested quite a few brands of subs in my 10K cubic foot room.  Some are simply terrible in terms of muddy concocted sound.   The worst one (for my space) was the Paradym monster 15 inch sub with way too much power; although I can say that it is a very sturdy well built piece of gear.   Nothing would tune it to the room, about all it did was rattle the windows; it was not musical at all.  The next worst speakers I used were a group of SVS speakers, again pure mud and phasing them was nearly impossible.  A few others were tested with limited success and then I brought in Bryston/Axiom subs and how refreshing!   Absolutely harmonious easy listening natural bass which blends perfectly with the main speakers.  I currently have 4 subs; the room is filled with fabulous full sound, no muddy issues at all and they are a snap to phase with the fully variable phasing controls.  I set them up initially and rarely touch anything.  I found the most perfect musical bass yet.   I did not concentrate on size, that is all large or all small.  I bought the size which fit the specific area for location in the room.  Two are set up at the 90 and 270 degree positions and another is at the rear 180.   The 270 degree spot is one where I ended up stacking a single 12 sub on top of a dual 12 inch driver sub; the stack is around 6 feet tall and fills the corner perfectly.   Up front are a pair of Bryston Model T signature triple 8 inch woofer main speakers and no sub is needed in the front.   I cross the subs at 150 hz so that I get all of the really nice upper range bass with the very low mids, that was key to the set up.  I have the front mains crossed at around 80 hz so that they handle down to the mid bass and don't do the heavy lifting.   My larger subs will handle very low range bass beautifully.

I am really pleased with the set up; the speakers were all built to order for me in real wood veneers with pleasing satin natural finishes. 

Very interesting discussion.

Not difficult but it is a process and the more of a perfectionist you are the more knowledge and tools you will need.

Depends greatly on the subwoofer (RELs are by far the easiest because of their passive radiator) and the speakers (speakers with lower output are harder to integrate unless you plan to high pass, which I will not do.

Two subs are more difficult, especially if you don't know the proper method, but the results are better.  

I would not integrate a subwoofer without a using some form of measurement tool- e.g. a microphone, RTA software and full bandwidth pink noise tracks.