If you are fishing for stripers, blues and inshore tuna then most would agree the first rod to own is a 9ft 9wt. At least that's what 99.9% of the practitioners today agree on, myself included. I tried 8wt, 10wt, 7wt; 8.5ft, 9.5ft, 10ft - but the right sized single hand rod for the region's coastal fishery is 9x9.
If you go to a double-hander, then a 12wt is a piece of cake. Frankly, I find many of the fish I hook to be a challenge even on the 12wt. I wouldn't want to try to land them on anything lighter than a 9wt personally, in fact even my 9ft 9wts are just barely in the game for big ocean species. Perhaps if the fish aren't challenging on a 9x9 then the answer is to find bigger fish