I think the Trevala S in the ML power is too lite for your app. Even the M would be marginal. How will you stop a biggie from heading back to his favorite rocky hole? I like fishing lighter tackle as much as the next guy, but not if its gonna break my heart.
I'm not saying that it can't be done with a very light setup - because it certainly can. Just this week I fished with Capt. Mike on his charter boat "The Captain's Table." Also aboard was Chef Nader Gebril - who fished with a teeny-tiny spinning setup so freakin' light, it would be more at home on an upstate trout stream. Yet he was high hook, out fishing BOTH Mike and I, with him landing a good amount of big tog to 8.75lb - along with several in the 6lb class on top of that biggie. Hey, what can I say? It happens. No one can be the King EVERY day, right?
So it can be done with uber-light tackle - with some luck, of course. But to me that is "stunt fishing," and not something that I'm all that interested in emulating - or recommending. So, in my opinion, if you are going with a Trevala S, then look at the MH.
Scout around, as there are deals to be had on the S series. Just this past Spring I was in Jigging World (an AWESOME place to visit, by the way!) and they were offering a good selection of the S series at 20% off. You almost never see that on Shimano rods. I suppose that it was because that series was being discontinued by Shimano, who now feature the brandy-new Trevala PX series - which I have not as yet seen.
Keep in mind that an ML in one rod series does not necessarily match up with an ML in another line of rods - even from the same manufacturer. Each rod series is unique and has to be evaluated as such.
The PX rods, like the older S series, are said to run approx $150-175, in that neighborhood, anyway. The Grapplers are a step up, in blank technology as well as the guide set they carry. Expect to pay another Hundie for a Grappler over a PX.
Thinking about your prior posts, perhaps the Grappler Type J ML would be OK for your type of fishing. When you do get to look at them, compare the ML and M, before making a final decision. The nice thing about the ML is that it can double as an awesome ocean fluke jigger - especially so if you need to cast about the boat on those slow-drift days. It excels at that type of use. I can say that from my own hands-on experience.