Personally I just use the provided headset and take it off at 18 and then use the speaker and hand mike. I have used the telex 5x5 pro and it works well if you get a good mold for your earpiece. I think that it gets pretty old having a big thing in your ear for a long time though.
Also you should be aware that it comes with both one and two plug configurations so make sure that you get the right one. I know the company provided ones have two plugs (mic and headset) on the md. I'm not sure if there is a plug up there for the single plug models or not.