This. ^ A custom tuner will want to know what mods you have, and will start tuning from there. That's the idea behind "stages." An aftermarket intercooler, for example, will allow a hotter tune than a stock one.
If you have no mods, the tuner knows how "hot" a tune you can safely handle. My tuner gave me several revisions until I was getting the best power possible with the mods I had, while keeping the negative corrections to a minimum for safety and durability.
The Dizzy flash tune is cheap and will be quicker than the Cobb tune. Definitely worth $75.
If you decide to do a few mods down the road, a custom tune will cost more, but will be totally worth it.