ML Descent-i vs. JL Audio F113

Hi,

I have ML Spire speakers in my living room (vaulted 22" ceiling). I can't decide whether to go with a matching ML Descent-i sub or the JL Audio F113 sub?

I use my system as 80% HT and 20% stereo. Should I get 1 or 2 subs? I am leaning towards 1 since the Spire puts out a decent amount of low end already.

Thanks, TD