New yes, a used U7135 will be significantly cheaper. An 06 R/T with the stock 2.82 gear and a canned tune will do 140 with a little left, so I imagine an 07's performance would be similar.I think a Diablo tuner will cost about $400. You can use it to bypass your engine speed limiter, adjust shift points and other things. I think it will help you get a few more horsepower but not a lot more? 125 mph is pretty fast. My 5.7 R/T with the Super Track Pack option will go 147 mph but I have never felt a need to even take it up to 125...it’s kind of a risky thing to do.