AR15 & M1A
Keeper,
Since it seems as if you are torn between the two rifles, I will not introduce any other rifle as a recommendation. In fact, I'll go as far to say that the AR15 and M1A would be the two rifles I'd own if I could only own two rifles.
I agree with the other members of the board, and would choose the AR15 first. Like Steve Smith, I own both. A few AR15s and a single M1A to be exact. Although I have not found enough time to shoot highpower, I am not oblivious to the notion that the M1A is a chore to keep accurate. In fact, I am still trying to find out what it does and doesn't like. My research has lead me to believe that although robust, the M1A is an extremely finicky rifle (accuracy wise). Not so with the AR15s, at least from my experiences. It is not uncommon for a bone-stock AR15 to shoot moa or better with "match" quality ammunition right out of the box.
A plus to the AR15 is that excellent quality pre-ban USGI magazines are in abundance, and can be acquired at reasonable prices. Plinker and "gourmet" ammunition is relatively inexpensive. AR15 gunsmiths are a dime-a-dozen, and the accessibility to replacement components is almost ridiculous.
Both the AR15 and M1A are fine rifles, and I would think that you would be happy with both. I said "both" because you ARE planning to get them both, right?
As to fun-factor, it's a toss-up. The M1A reminds me of the first time I ever fired a rifle due to the fact that it is a more modernized M1 Garand (first rifle I ever fired). The relatively comparable recoil of the Garand, and the way the rifle makes that certain ringing sound as the action cycles bring back fond memories of the 7th grade. The AR15 on the other hand is a dream to shoot and brings back memories of the 8th grade.
El Rojo brought up an excellent argument concerning the future availability of "black rifles." I can only feel his pain. Being a California resident was the single factor of my "stock piling" of AR15s. These rifles are almost an addiction. I have never met a single person that could have JUST one AR15.
As to the C-MORE, I cannot comment. My only experiences with the "red-dot" styled sights are the Aimpoints and Trijicon Reflex2s. The C-MORE appealed to me for a while, but thought that the Aimpoint and Trij were a little more robust in design.
Hope this helps?
Jim