One thing we are all guilty of, including myself, is that we don't plan for the future and wind up spending more money than we need to. After slowly moving up the chain, 550, 750, 780, I finally decided to run FIC 1000cc injectors on DSMLink. I really haven't seen any drivability problems with bigger injectors in the sizes we talk about. I have heard idle is tough to tune on the 1600cc injectors, but no real life experience here.
Ask yourself this, what is the most power you want to make, what is the biggest turbo you will ever bolt up, etc and buy what you would need for that. Don't buy for today, buy for tomorrow.
The FIC injectors that I've had seemed to work great. They are what most of us run.
If you swear on "Scout's Honor" that you'll never go bigger than a 50 trim, 650-750cc would do it. I would lean more to the 750cc if you can tune them in on your set-up. Gives you a little more room to grow.