This is a very common question, hence the lack of answers.
Swaybars, more than anything else, govern the front-to-rear weight transfer as you throw the car through a turn. Look here
for a lecture on the subject.
Once you begin to develop some serious grip, your body will begin to flex at weak points near where those forces are transmitted to the car. The biggest weak point in this regard is the bathtub frame your engine sits in. Adding a brace across the top can help this quite a bit.
The second place is the trunk and rear, lower subframe. You can also get braces for these.
The mount of flex is proportional to the grip. That means you don't need serious bracing without serious grip.
I also STRONGLY recommend that you upgrade your shocks at the same time you install your springs. If you don't have the money for good shocks yet, I recommend letting the springs sit.
As for brands. Swaybars are a hunk of spring steel with a few bushings. Brand matters little.
Brand matters even less for strut braces, except the good ones are not hinged, which makes fitment expensive and tricky.