If (as per your comments) you're looking to deaden road noise as opposed to engine noise then you aren't going to see much improvement from installing/up grading the under-bonnet sound insulation.
The sound deadening under the carpet and inside the doors is more the area you want to look at - however there's a great deal of effort involved there in taking carpets up, disassembling door trim and removing the existing deadening material and then replacing it. And even then you might not see much gains. There will be sound deadening material there and you will have to remove it in places to get the new stuff to fit.
Overall it's possible spend quite a lot of cash to get stuff there that is going to be significantly better, something like Dynamat is pretty decent. Even so you're still going to get quite significant sound levels leaking in through the windows, the door gaps and so on.
Another area that's worth considering is reducing the noise generated in the first place - you can get tires that are quieter (the noise rating on tires is based on a drive by test but as a rule of thumb the quieter-rated the tires the less noise in the cabin too) and fitting smaller wheels with larger profile tires will make a big difference too. Also worth thinking when you last had your suspension bushes refreshed - the car is ~7 years old now and as bushes age and the rubber hardens they absorb less vibration and transmit more noise to the cabin.