If you want your food to taste like restaurant food, use Kikkoman or Lee Kum Kee. Both are good, basic soy sauces, and are very cost-effective for cooking mass quantities of food. Plus, it doesn't sound like you've got a lot of time on your hands to do any taste-testing of your own. Personally, I don't mess with low-sodium anything--I just use less of it at the outset, adding a sprinkle or two just before serving if necessary. How much is "ample?" Every major grocery chain sells Kikkoman by the gallon and half-gallon.

for a low down on shoyu check this website out:

http://umailabs.com/word-of-the-week-shoyu-%E3%81%97%E3%82%87%E3%81%86%E3%82%86%E3%80%80%E9%86%A4%E6%B2%B9/

I would only use a naturally fermented soy sauce, i.e., one that includes only ingredients that I recognize (soy, wheat, salt, water). Even the "best" brands in Chinatown are full of things that affect their taste. I know. I've been experimenting with various Chinese and Japanese shoyu and tamari products, and always come back to the naturally fermented ones. The three most easily obtained brands of good, naturally fermented natural sauces are: Trader Joe's low sodium (my first choice, actually, for flavor and how well it performs in cooking), San J (Tamari and Shoyu), and Eden Organics. If you want a sweet sauce, add a pinch of your own organic sugar. ;o)

This is very helpful.

This is from chinatownconnection.com:
In general, Chinese soy sauce tends to be very dark and salty with an earthy aroma,” Tropp says. “Japanese soy sauce is brown-amber in color, sweeter and meatier and has a lighter aroma.” Chinese black soy sauce, which contains molasses, has a very dark color, is thicker than regular soy sauce, and has an intense flavor. “This is a far stronger product with its own flavor dimension. It’s a much less adaptable ingredient, and not for the Western cook just beginning to use soy sauce. It’s good with cold noodles dishes and mixed with regular soy sauce in stews and braises. It also can be sprinkled into sautés.”

Japanese soy sauce (shoyu) is sweeter and less salty than Chinese -- so bear that in mind. And anytime I cook with full sodium soy sauce, I usually regret it. It's much easier to control the salt level as you go when working with low sodium. It seems many recipes assume low sodium, without saying so -- has anyone else found this?