I would definately do the small bit of modification to install the 6.5" set. In my opinion there is no best set just a long list of very good speakers out there and some personal preferences. Focal is an awesome brand of speakers. Some others to consider would be Hertz, Morel, Hybrid (HAT), ect. I've been in the car audio industry for over 20 years and my opinion is spend as much as you can afford on your front speakers, then pick the rest of your gear around that choice. If I were working with a $1300 budget I'd spend almost half that on the front speakers, get a good quality co-ax 2-way for the rear and then spend the rest on a nice 4-channel amp to drive it all. Some quality amps to consider would be Audison, Zapco, Arc, Mosconi, ect. This is just my two cents. I hope it helps!
Here's a link to my F150 build: http://www.f150forum.com/f4/smd-audi...0-build-71259/