Your instructor will sell you Dave Clarks as thats what they get as cheapo or freebie. DC have a fantastic marketing machine.
I have a set of the in ear plugs here, you have to get them molded to your ear canal. They are not very good, and give you ear wax problems as they cause you to get hot ears!! I also found if I turned my head sharply to talk to pax they came out.
Bose-X were the best. Pilot DNC were not bad. I have 7 sets of DC's and they all have different compatability problems!! I have them numbered so I know what works with what! The main problem is when you use them with an SPG400 or on the side tone of a radio, the have imepedance mismatch issues. Using them through a GMA430 is one of the few times I never get a problem.