J&M Elites and Edsets 3G will run around $200 each for the system and cables. Helmets are your choice but some are more difficult to install the com system in.
You should decide what com system and helmet you want, then call around or surf the web to find a dealer that can integrate the system into your helmets. Many dealers will install for free if you buy the gear from them. You should expect to pay between $600 - $1000 for the pair, new, not including shipping, tax, or possible installation.
You can listen to the radio on the outside speakers and need nothing, but if want to use the intercom then you need a headset. CB doesn't have anything to do with either. CB is great if you ride in a group. Price depends on kind of helmet you want and quality of headset. Open face helmet of full face or flip up. Headset run from $79.00 to over $200.00. Check around because prices vary a lot. Check for sale board also, sometimes you can get a good deal on a slightly used helmet with headset.