I would consider doing what you have already thought about, which is use the OEM and get a 4 channel amp, like the BT4180 as suggested by mrhdvrod.
Never mind, I now take that back, while I do like the idea, I would have taken the OEM and put it under the TP and put the BT4180 in the fairing, but then it hit me, you have a '12 CVO, which means you have the 160w amp, so now I have to say get rid of it.
You should decide how much you are willing to spend on doing this first, and then look for the options you have in that range. I have put together lots of systems, and when I am looking to put together one for me, I never really think about the cost because I already know that (at least for me) it is going to be what most consider a lot of money. For most though, the first step should be, what are you willing to spend, not what do you want to spend, but what are you willing to spend?
I think if not out of the price range you come up with, then I would look at something like a BT4180 with a BT2180 along with the speakers, to save some money you could get the 4180 and an RF pbr300x2 and some infinity, focal, or another brand (although the better focal line will not save money). If still too much then I guess you are getting closer to two RF300x2 (or even three), and some infinity or this range of speakers.
If staying with HD then I would get rid the amp now, and get the newer amps, if you get two new ones, you can put one if the fairing amp get the second one with the TP installation kit, and put it under the fairing, you may have to get another set of speakers and run eight.
were will If staying HD is important than get two of
No, not enough room for two amps in the fairing, unless you give up a few of the add ons, but you can mount an amp under the TP which is the best way if it fits, or you can install one in a saddlebag.