I'm going to go a little techie here and these comments are intended more for those who are new to fly fishing or are trying to get better. I often see posts regarding rod choice for various species and the following discussion might help some make a choice.
As I don't eat fish, just don't care for it (wish I did), I want 100% of the fish I catch to survive the release. I need to whip 'em quick, take a pic and get them back in the water asap. Doing this requires using the rod to produce maximum pressure on the fish. So, I employ the technique wonderfully illustrated by Andy Mill in the video linked to below. In the video, Andy shows how to use the rod to apply maximum pressure on a fish and, conversely, how one might use the rod that simply applies pressure on the rod and not the fish. Andy is fishing for tarpon, but this technique absolutely scales down for whatever we are chasing around here.
Andy Mill's Fish Fighting Two Minute Masterclass. This is an awesome video.
Back to what rod I use: For the fishing I do around N. TX, I pick my rod based upon the fly I intend to cast and the amount of wind I anticipate, not based upon my target species. For carp, sand bass and creek hybrids, I use a 4wt. Plenty of rod if you employ the technique shown in the Andy Mill video. As I said, for striper I use a 6wt, but that's because I'm generally making longer casts and I'm fishing places that are unprotected from the wind. If I were casting really big, fluffy flies and targeting huge largemouth (like our buddy who's initials are RH), I might kick it up to an 8wt. But, 99.999% of the time that I'm fishing my home waters, I'm fishing a 4 or a 6.
If one uses the technique demonstrated in Andy's video, one can quickly land an 8 lb striper on a 4wt rod. Conversely, if used improperly, one can easily break an 8wt rod on an 8 lb striper or, by not applying pressure on the fish, take forever to land it.
In his video, Andy makes no mention of his reel or terminal tackle, so I want to add a couple of comments. When fighting big fish, pick a leader that is up to the task. Then, crank your drag down as tight as you can without over stressing your leader. Let the fish fight the reel while you apply pressure using the butt of the rod.
Regarding leader: I'm cheap and don't want to spend money on several different spools of line or tippet, so I only buy one leader material for all of my home water fishing. I use Seagar Tatsu, 20 lb flouro. Weather I'm fishing for carp, sandies, hybrids or striper, that's what I use. Right now I'm wondering if Texasflycaster is thinking, "20 lb for carp?? Really??" Like I said, I'm cheap. The 20 lb line has the same tinsel strength as the core of a 6wt. fly line so, if you do this, be careful about hanging up.
Here's a shot of a 9 lb hybrid I caught on my 4wt. It took be about 4 minutes to land. This is just one of the maybe 200 decent hybrids I've caught on my 4wt over the past couple of years using the technique described by Andy in his video.
I hope you find this discussion helpful.