bass in the room

How deep's the primary null at your listening position and at what frequency? Just how "ragged" is the frequency response at your listening position between 30Hz-150Hz? If significant, move your sub or listening position (or both - whatever's most convenient) to where things measure best. If that's not feasible/sufficiently corrective, EQ with a Rives Parc ahead of your sub. Bass traps will help somewhat, but good ones (ASC full rounds, etc) are expensive and were far from curative with my tray ceiling. I run stereo subs with reasonable output above 100Hz so they are kept alongside the mains, and I am unwilling to change my listening position; therefore I had to bite the bullet for a PARC. Kept ahead of subs only, it's transparent and reasonably effective in a very bad room for bass.

L-shaped rooms are bad for proper acoustics, and cathedral ceilings are bad for proper acoustics. You have 2 bad strikes against this setup. If you can't move the system to a different room, you have to just work with what you have. I had the same setup in my previous house. I had an acoustic engineering company do very expensive sound management installations. In the end the results were good but expensive and professionally done, with little wife acceptance.

I had/have a similar problem. In my crummy room (vaulted ceiling, open at the top to kitchen/dining area) the N802's exhibited a pronounced dip at 60-70hz which robbed the bass of impact. The sub doesn't help because it reinforces the areas where the N802 is already strong (below 40hz). So far, I have never found a solution.

Right now I'm trying different speakers and room treatments. The new speakers don't go as low in the bass which should give more flexibility in maximizing placement of the REL B3 to achieve the bass I'm looking for.

My perception of room treatment is that it can alter minor problems but not correct major frequency abberations.

You might experiment with different subwoofer placement.