As far as the feed neck goes, i would definitely go with the LAPCO Direct Feed or something like it, it may be more expensive, but having used both. The LAPCO will be more secure as well as more stable. Using the Body from CCI would make you need to buy those cheap Plastic feed necks, which if you are hard in your play as I am you will realize that having to buy those things over and over again is a pain in the posterior, Also if you buy the CCI Body, you would have to change the body itself if you decided that you want to play stock for a game, instead of just unscrewing a single screw and screwing the horizontal feed back on. Oh, and one other small point on using the 50 rd hopper, it's small and light but do you really want to add another two inches of height to that by using the plastic feed.
Oh also, as a brief side note, I found the Adapter that I have been using. You can find it here....
http://www.pmpind.com/Detail.aspx?PROD=96334&CAT=3382The thing about it is, it's just the adapter, you can buy a smartparts ION feed neck for it. this one seems to be cheaper especially if you have an adapter already.
Also you can find it for sale on this site. A few bucks off.
http://www.smartpartsparts.com/PMP-Industries-Feedneck-Adapter-Phantom-p/1691.htm