Also take into account (at least with my experience) that the adapters will fit real snug against the speaker. This makes them sound pretty crappy because they do not have enough room to vibrate for bass. I put a few washers in to space it out, and it was a tight fit in the back, but it fit. FYI my speakers are Infinity 6X9's.
Jesse
Fort Worth
Also the unused 4X10's fit great under the seats pointing toward the back seat.