I agree with you that Knorr makes the best soup/stock bases.
Unfortunately, Knorr makes two kinds of bases. the ones that they sell in Europe, which I prefer, are more natural and not as strong tasting. The ones they sell in the States have more flavorings because they believe that the American market demands stronger flavors.
One way I use to intensify the taste of my chicken stock is that I roast the bones of the chicken before I put them in the stock pan. It makes a lot of difference.
If you are talking about professional base, I like Minors. If you are asking about what is readly avaible to the public... there is a base product, I think it is called "better than base". I usually see it in supermarkets.
The thing is when you are using base, read the directions on how much to use per gal. It is real easy to use too much, and you will taste it.