With those speakers the 2312 should be fine. As long as it has all the features you want, you really wont need to upgrade to the 3312.
These are all the upgrades to the 3312 from 2312
Dual HDMI outputs that can be active simultaneously
Pre-outs for all channels
Audyssey DSX with speaker terminals for all 11 speakers (however only 7 can be active at once)
AL24+ processing on FL/FR channels for greater 2ch music fidelity
A dedicated PHONO input with pre-amp stage
Ability to scale sources to 1080p/24
Ability to cross-convert analog video signals (e.g. s-video in to component out)
Enhanced multizone / CI capabilities:
--- 3 zones instead of 2
--- Composite video output to Zone 2
--- Ability to send digital 2.0 PCM audio (optical/coax only, not HDMI) to Zone 2/3
--- dual 12v trigger outs
If you don't need any of this stick with the 2312.
These are last years models as the xx13 models are out now. You should be able to get better pricing than that.
Or if you don't mind buying refurbs accessories4less.com can save you a lot of money.