Unfortunately I don't believe the 2312 has pre-amp outputs to connect the XPA-3.
However, after casual perusal of the Verus Forte speakers, they look to be of relatively low sensitivity; for example the center is rated at 85dB, which is a tad below average. IOW, they'll need more power to get to a given SPL than a more sensitive speaker. Something like the XPA-3 or 5 could have value, depending on how loud you want to listen, how far you sit from your speakers, etc. This SPL calculator will give you a rough guide as to how much power you might want:
http://myhometheater.homestead.com/splcalculator.html
Also, instead of the 4308, I'd be looking at the 4311, for which some pretty good deals can be found at the moment. In addition to reasonably good amplification for a receiver, it also offers Audyssey XT32 with SubEQ, which could be useful depending on your room and your setup plans.