Have you considered ingredients? What grains are you using? I love my LHBS because he stocks top quality grains, stores them very well, and refuses to substitute for lower quality. I feel the good quality shines through in my beer. I costs more, but quality has a price.
IMHO, sour mashing is not a solution to your problems. Certain styles demand a sour mash or fermentation, the styles you are having trouble with do not. If you want to do a fun brew just because, that is one thing, but I would not expect an experiment brew to fix your other problems.
If I were you, and I wanted to make a truly great beer, I would pick a beer style. Find the best recipe I could for that style. Research the best way to make that beer. Then do it. If you notice a fault at the end of the day, try to fix that problem (e.g., recipe, mash schedule, ferment temps, yeast choice, etc.).
For example, if you like wheat beers, do your next one with a very traditional recipe and do at least a multi-temp mash with at least one decoction.
I don't mean to discourage you, I just don't see how doing a sour mash will help any of your other beers.