I have the rod in a 9wt, and the Airflo ridge striper line does well on it. I've also used the outbound short and rio striper lines, but I'm pretty sure that when I purchased the rio striper, it was still rated by line wt. I bought it in a #9, and I can't remember what the grain wt is, but I think it's 1 1/2 or 2 line wts heavy according to the AFFTA chart. At any rate, the outbound is actually more like 2 1/2 line wts heavy, but being a shorter taper, you don't need to carry as much in the air to cast it. The E3S will handle any of these, but the OBS is what people call a "chuck and duck" line. You really only give it one or two false casts and a good haul. The rio striper will cast weighted patterns well, but it has a tendency to throw a more open loop in my experience. Both are good for schooling fish that surface fast and go back down, where you don't have time for 3 or 4 false casts. Neither are ideal for quiet presentation. The Airflo line in a WF9I is the best all around line that I have used on the rod so far, I use the rod for landlocked striper. If you are new to fly fishing, or if you have a lot of wind to contend with, the outbound could make life easier, but in a WF6I/S6, it will not be a pleasant cast. If you can get away with it, I much prefer a sink 1 or 3 tip. I've used the OBS in all different wts and configurations, the one I like is a WF#F/S3. But I go down one line size if I'm going to use it.
Keep in mind this is on a 9wt, I know the 8wt is pretty much the same rod but lighter duty, from using my friend's, but I can't speak as to whether the 6wt will fish the same with these lines. I will say that the E3S is a great value rod. It has an excellent blank, and is pretty much purely functional, with a no frills design.
One more thing I should mention is that I've found the Airflo line to be the best performer of the three in cold weather/water. It handles air temps in the 30's and water temps in the 50's with no issue. The Rio lines can have a tendency to knot up and benefit from a good stretch periodically.
