Ok I get from your post that you want to show off your abs. Congrats on your cardio health and you low BF%, as you are basically already at the six pack point. All you need to do is lower your body fat a little bit more, and doing crunches is pretty much useless for that. You'd burn more fat by going to the gym and lifting, then running. Lifting will burn up all the glycogen in your muscles and leave only fat for your to burn for energy.
However, if you want to get "Huge arms...etc" you're not only going to have to eat more, and probably lose sight of the six pack for a while as well, but you're going to have to train your legs! read
http://www.discussbodybuilding.com/Stop_fking_around_and_lift_like_you_mean_it/m_127347/tm.htm I read in another post something about you need to gain so many pounds to add 1 inch to your arms. Supposedly gaining weight in the legs is the easiest, and if you don't train legs you're at a serious disadvantage. However, it sounds like you are a runner and would be against doing that, and I do have a friend who runs a full marathon in less than 2.5hrs and he started lfiting and has huge arms and upperbody for his frame.
I'd reccommend lifting in a regimen that you like, and then running afterwards. Just don't overdo it - Say your lifting schem takes 40 minutes, run no more than 20 minutes. You are already on the right track being here though, and wanting bigger muscles. The more muscle you have, the faster your metabolism, so if you DO decide to forget the abs for a bit and try to pack on muscle, you'll find it's much easier to burn the fat once you have more muscle. If you just decide to try and burn fat right now, it will be a little bit more difficult. So try to just burn the fat right now, by basically lifting then running, then if it just seems too tough, switch to packing on muscle and try to burn the fat again in a few months. Keep track with calipers and judge you're progress by overall fat loss, not by how many crunches you are doing. I'm sure running is working your abs enough anyhow.