I think you will be happy, and it is the gift that keeps on giving. (free re-flashes)
You should see an immediate improvement, but the tune will also make any future mods better.
I have the Magnaflow, and love the sound, but it is not a performance enhancing mod. I wish I had the funds to jump on the "George" sale right now.
At $300 it is easily the best bang for the buck currently available for the Crossfire.