I would hate to see you trip over a dollar to pick up a dime. Or in this case trip over several thousand dollars (and several days of labor) to get a couple hundred dollars worth of benefit.
I have done things at both extremes of spectum, and was happy with the end result both ways. How, you may ask. Because I knew exactly what I was after, and took my time making a game plan. I knew what "satisfied" looked like before I started. I didn't just throw everything including the kitchen sink at it hoping end result would make me happy.
My advice would be focus on where the annoying sounds are coming from, and see if you can minimize them. If it is an interior panel, place your finger on it. Does this sound stop or get quieter? If you feel like the noise is coming from the fire wall, place a heavy blanket in the floorboard. Does the sound get quieter? If you feel like the noise is coming through the doors, put some cushions against them. Etc. Wash, rinse, repeat. Start with the most annoying noise and work from there. If you are due for new tires, now would be a great time to check which ones have the lowest noise rating.
Short of very cheaply made cars, I have found most only need treatment in a few places. Anymore I just plan on doing a full treatment on the doors as the mid basses are in there, and quite a bit of road noise can seep its way in there also. After that I place pieces of foam behind any plastic panels that are vibrating. (what your finger is mimicking, when you're pressing on them, only from the backside) If the minimum you listen to your stereo at is 75-80 dB, and the road noise is 70dbs....your golden! If it helps you sleep at night to go to the extreme, by all means go that route.