One Sub or Two?

Hey folks, looking for some thoughts here on subs…

Putting together a system with B&W 801 D4s and a HTM81 D4.  I don’t think B&W makes the best subs necessarily, so…

1. Looking for recommendations for other sub brands…I’ve heard good things about REL for example

2. Wonder whether I should get one “really good” sub or two “pretty good subs?”

System is for 2 channel listening to classic rock and also 5.1 audio for home theater purposes.

McIntosh amps and pre/pro.

Many thanks in advance for your advice…I appreciate it!