HELP - Subwoofer placement

Hello everyone.

I have recently decided to experiment with a subwoofer for my system (mainly audio, little HT) and dug out my old Definitive Technology SUB1000 from my now retired HT system. My room has a quite inconvenient L-shape with ver few options for speaker placement. I have used my kid’s drawing program to describe it as best as I could below where my two ELAC Navis ARB-51 active bookshelf speakers are the red squares (too far apart but little I can do about it, also for wife-acceptance reasons). The sub is currently in the purple square and I sit in the black L on my corner sofa. Grey squares are other potential placement options. The big brown rectangle is a massive brick fireplace. I forgot to draw a large cabinet sitting directly left of the sub in the guest dining area of my room (ie no man’s land).

Considering the improved SQ despite (i) potentially poor current placement/tuning and (ii) decidedly poor sub quality (much more of a big HT boomer), I have now just bought a used REL T7 (1st gen) which I will be getting next week.

Questions I have are:

1. If using one sub only, where would you put it?

2. If using two subs, would you use the two grey positions or right grey and purple? I read that opposing “corners” can be helpful to get rid of nodes

3. Do you see a lot of value in adding a second decent sub (thinking REL T5 to sit in the right, closed off area with the T7 to power through the more open space on the left)? IMO keeping the DefTech sub will only negatively affect the SQ of the T7.

Many thanks already for your views. Jokes about my drawing abilities of course welcome! 🤣