Since you've only got 1kw on deck, I'd go with the xd8's. You'd need more power than you have for the hds208's and vfl8's to get louder.
The xd8's can take that all day and give you plenty of whoa lol. I've given them alot more than the pr1000 can put out. My ssf was properly set, and when I was pushing them too hard I backed off the volume...never had an issue. Out of all the boxes I've tried, 1.55@32-33 hz where they're the happiest. I was between 140-143db with both the aero and slot port boxes on 1000-1200w
Here's a couple ****** videos playing decaf. Fwiw, I took the hds212 out after a couple weeks and put the xd8's back in. The Sq was on 1200w rms and the xd8's sounded better, was alot louder, and dug lower.
[YT]