I purchase a lot of fish from various vendors and have been to I&S a few times over the years.
I would never purchase anything from them as the quality and quantity of the poor seafood gives question to how they source and control all the stock.
Fresh Farms is a step up and the fish on the center counter that is usually filleted is usually very good quality but the whole fish on the back counter is usually substandard.
But as Posted you must judge each lot of fish on its own merits.
H-Mart has good live fish and shellfish but I believe that much of the filleted and whole fish have been treated with preservatives and don't purchase it.
My source in Milwaukee has excellent quality, sells no thawed previously frozen fish but that comes at a significantly higher price but is sometimes the only source for superior fish other than Mitsuwa which has a limited supply of fish from Japan (non-sashimi quality).
Yesterday in Milwaukee at Grash's 'dry pack' sea scallops were $20.99/# and dry packed bay scallops from Mexico were even higher but the quality is excellent.
I travel with two large coolers in my wagon on my purchasing forays to Chicago and environs and have been doing this for a couple of decades. If it looks good, i purchase a quantity and we wrap and freeze ourselves.
My experience comes from growing up in Massachusetts and spending summers in Maine where truly fresh fish could be caught or obtained and has formed my purchasing body of knowledge.
My favorite source of fish and shellfish is Browne Trading but the shipping costs have made that source all but prohibited.-Dick