6.5" Polks can be made to fit.
I currently have a great sounding pair of DXI 651 Polks. It is a deliberate process but not hard or time consuming. Just detail work.
Make a template out of either laying the oem on the 6.5, trace the outline or build a cardboard template.
2 small areas on both speakers needing trimmed.
The MMs will also fit with modifying them. 20150228_103206.jpg
Jim