You're better off asking for help at DIYMA forum, should be able to find some guys local-ish to you who have RTA and can help you dial things in.
Or get yourself one of those head units which has auto EQ setup with a mic.
I'd agree that IF you can find a shop competent to do the job they're going to charge high and at the end of the day you still may not be happy. Flat response sounds pretty bad and what deviation from that you'll like best is purely subjective.
Then again, if you just mean gains and crossover settings, anybody should be able to help you with that, or at least explain what does what you you can tinker with it yourself.