Wilwood has excellent articles on both residual valves and proportion valves. When to use them and why.
www.wilwood.com
www.stockcarproducts.com also has some great tech articles.
The 944 or stock dual MC question comes up alot. It is probably about 50 50 divided on what you use. Both camps seem to like the outcome either way. Read the articles and decide what you want, other wise you won't be happy.