BTW, OP, get the Levi. Should be the last amp for your comps you'll ever need. That or a Zuki. When I'm ready for it, I'll be going with one of those. Have to find the right HU/processor first, though.
Best to have the active controls up front as you WILL find yourself tweaking everyday for a long time to come. Better to be able to change there and listen than hop in the back and hop back up front for a listen.
Rear fill has way more benefits than a lot of people like to make it seem. Rear fill completes an SQ system and, when implemented properly will sound better at the driver's seat than to the rear passengers.
However, if you're running active off the 80PRS with subs, you will not have extra preouts for rear fill. The only way to do rear fill would be to somehow split the signal from your mids to an amp for the rears but to get the full effect of real rear fill, you would need to integrate a mini DSP with the rear fill plug in that will properly process the rear signal and also allow you to delay them beyond the Haas effect, thus creating a larger listening space.
If in the future you decide you would like to add rear fill, you can upgrade to a 4 way HU or external processor or simply add the mini DSP into the mix. But, no need to do that right now as you may be satisfied with just the fronts.
Its always recommended to perfect the front stage before moving to other speakers anyway. Otherwise things just get more complicated with more drivers.
Once the DSP does the differenced signal and delays them about 20ms behind the fronts, you're pretty much good to go and not much tweaking should be needed.
But, I still say go with just fronts first. Just don't count out the possibility of rear fill even on your setup.
I'll probably just end up running my CDT HD-62CF's up front and nothing in the rear for now. Planar tweets look really enticing, but cost money
Only way you would be able to add rears and go active is adding a separate amp for the rears.