I have an '08 MCS and the noise was so bad I couldn't use the bluetooth phone.
I installed some sound deadening material from second skin. this was a very significant improvement but took a lot of time (two full days) and it was about $500. I installed Damplifier Pro and Luxury Liner Pro. The improvement to the stereo sound was Great. the reduction in noise was good too. This is a labor intensive project and you have to have time and some skills. remember to disconnect the battery first or the airbag warning will get confused among other things, and the service guys will get all pissy about modifying the vehicle. I did the wheel wells, doors floors & hatch.

A few weeks later I was still not satisfied so I switched tires. This was a more cost effective and significant improvement. My runflats were wearing well, but noisy and very choppy handling. Stock tires were 205/45/17 and I went with Goodyear Eagle F1 All Seasons in a 205/50/17 size. they had 45 series but I went a little taller for a few reasons. These tires are excellent. much quieter and handle far better.

My recommendation is to switch tires first because they help with both noise and handling is far better. Then if you still want the car quieter do the Damplifier/Liner project. If you want a simple project or want to approach in phases, here is the priority:
1) Wheel wells - easy and this is where a lot of noise comes from
2) Back Hatch & "trunk" floor - if you run with the seats down alot.
3) Doors - most difficult, but this is where you get the added benefit of a great improvement in the stereo sound.
4) under the seats & floorpans - these are very well insulated already and frankly I don't think you gain much.

if you have questions feel free to email or call me.
Steve@straubconsulting.com 503-481-6509