I do quite a bit of headphone listening lately, but only use IEMs. How would the Crack work with them? My current favorites are Shure SE210s and the amazingly comfortable Klipsch X10s.
Over the ear cans don't work for me as they irritate/rub my right ear and can only be worn for 20 minutes without pain.
Building the kit looks like a fun project to get my grandson involved with.