Your sub experience: Easy or hard?

With a high pass crossover it was very easy in multiple rooms and systems. Without it , it was very hard and honestly never right.  

I’d say it was maybe a 7 on a scale of 1-10, 10 being the most difficult. Difficult in terms of finding the best placement for sound quality and aesthetics. I think I found the best setup for the room I have them in. I could probably spend more time but I have them dialed in pretty good right now. They really disappear and were definitely worth the time integrating them in. 

Recently traded out my older REL T2 for two smaller REL T5x's paired with B&W 805 bookshelf speakers.  Significant sound stage improvement and separation, plus a more balanced low end.  It does take a little time and effort to get the integration right, but the results are worth the effort.  Plus it is fun to do. You will be able to do this.  PS wife walked into the room once setup and said I hate to say it, but it does sound better.  No finer praise indeed. 

very very easy with  lyngdorf amp 😁

I don't think there's a standard answer. It depends on

1. The size of your room.

2. Room treatments.

3. The size (lower frequency extent) of you main speakers.

4. Your requirements, whether it be gentle underpinning or thumping bass.

In my case my room is treated and my main speakers go down to about 70Hz 

I prefer gentle underpinning, and with the main speakers disconnected I adjust so I can barely hear mail vocals. Dead easy