At what horsepower should you look at going to 1 and 7/8 headers or larger?

I have 1 and 5/8 shorties on my 383 and I know its hurting me but I dont want to go too big. Would 1 and 3/4 longtubes with an x-pipe and bullets suffice? Or could I just put in a cut out and be done with it?

 

You running a cat and or cats? How about an ORP and a cut out for now?

 

I've got a 3 inch y-pipe and the cats have been gutted long before I got the car

 

From what Iv'e read, gutted cats are not a good idea unless they have a pipe inside to make it a straight shot thru the cat. Seems like that would make sense, but what do I know? Since your cats are gutted I take it you aren't worried about emisssions, correct? For now if I were you I'd lose the cats and run a cut-out for track use.
Unless you have big HP, 1 7/8 are overkill. That and the fact you will have fitament problems along with all the noise that comes with bullets that are going to dump underneath the car.