You can easily fit 6x9s in the front. The rear requires a small amount of modification.
The kenwood 6x9s are the deepest 6x9s i could find. Any 6x9 will fit in the front without mounting depth problems.
Most of the JBLs I have ever heard or used have not had real good bass extension, but generally are louder then other brands. Except for the JBL 545 which is, IMO, the best 6x9 ever made. Incredible bass extension, huge power handling, great highs.
