I am about to order the rack and pinion setup and need to know which rack to get. Standard of Quick ratio.

Any suggestions?

Does the quick ratio rack have a significantly harder steering effort?

This will be on a street car that will be driven fairly aggresively.

The effort of the 15:1 is no more than the 20:1. Both are easier than the stock steering without PS.
With the special we have both are the same price so you certainly want to go with the 15:1

-billy

Even though the post is old I'll respond so theres an extra point of view.

The 15:1 ratio rack is extremely easy to turn with one hand while sitting still. Don't worry about the horror stories people talk about when having a manual rack. A properly designed manual rack is just as easy to turn as a power steering rack. This is a properly designed rack and suspension. The quality is higher than almost anything i've ever bought for any car I've owned. Buy stress free.