Is the speaker 7" diameter or the cut out in the panel 7"?
JBL do a 8" Sub GTO804 8" Subwoofer that fits a cut out 7" in diameter! Only £39.99!!!
GTO804 8" Subwoofer
JBL are owned by Harman International who also happen to own Harman Kardon!!! Can you see where this is going? ;)