Hi John,
Welcome to the forum.
Your are essentially setting up a large listening room where you and possibly a handful of others will listen to Jazz and other genres of music for critical review. - correct?
Given this scenario, I believe the "Pro" speakers are overkill and not quite right for your setup.
For subs I'd look at the Table Tuba and THT (Tuba Home Theater)
They will go as low as you could want and are still plenty loud.
Especially if you're planning on building 2 of them.
I was testing out a Table Tuba in my shop yesterday 20 x 30 and it was rattling the garage door pretty good.
Have you considered the David's for you main speakers? I think they would be fantastic for your setup. I can't say enough good things about them. I absolutely love mine for stereo use.
Kevin
Authorized Builder - Phoenix AZ.
Main Rig - 6 DR200s - 6 T48s (30")
SLA Pros for the smaller stuff.