There's also coconut milk based yogurt (by So Delicious), I've never tried it, but I tried the coconut milk and I wasn't impressed
I would try experimenting with different brands of the soy yogurt. Silk was my favorite at one point in time, but then I tried Wildwood Organics and now I won't eat anything else.
As far as replacing feta cheese, you can try using tofu as a replacer, I find that it works for me with regards to lasagnas and other dishes that would call for feta cheese.
The worst sin toward our fellow creatures is not to hate them, but to be indifferent to them. That is the essence of humanity.