One of my subs has two speakon connections so you can run one from it to the 2nd sub. When wired right that puts them at 4 ohms. I did it that way and bridged the amp but decided to go to 2 ohms and use both channels.
I think the sub cabinet has a lot to do with it. The Rythmik FV-15HP uses a 600 watt amp. That's a no joke sub. I don't think I get anywhere near 600 Watts at the levels I listen at and they hit pretty good.
Oblivion will be my first one. With the subs off I've heard better mid bass punch. With the subs on I get all the punch I need. I think where these really shine is their clarity. Vocal are very nice. I think some folks will have a hard time getting past the looks. Being that visuals can have such an influence on our ears. They sound far better than their price tag IMO.