I was wonderig if anyone has had any luck adding an amp to their factory h/k radio to get more volume.

 

THe H/K system is difficult to upgrade. THe stock "boost" system is easier (as it doesn't have an external amp/dsp). Both have been done successfully, however. Read through the navigation / audio forums.

Also, try searching for the "HK enabler" or "H/K enabler". There's been much written about this.

Good luck!