Uh... It's sorta obvious but yeah. DHD and Inspire are just the same except the Inspire has its own exclusive features from AT&T, Stuffs like Dual Mic's (For noise cancellation and I don't know if it works as a stereo recorder), and having different radio's.
Just flash the inspiremod for the specific rom (E.g. Flash the ICS inspiremod for ICS roms, and etc.etc.)
Some ROM's doesn't include Inspire 4G support though, so flash the inspiremod and see if it gets better. If worse, then try NOT to flash it.
For more unlocking stuff if your phone's pretty new, use the Advanced Hack Kit. It's quite useful. :3