Is this the correct solution for me?

Hi there!
I'm upgrading to CS5 and my site is on a PHP 5.3 server with MySQL 5.0.77 so I need to adapt a user registration system I built with ADDT to the WebAssist tools.

I have a password protected directory of my site. Within this password protected area, there is a PowerStore 3 store. There are also other custom pages within the password protected area.

I have an existing user registration database with SA1 encrypted passwords. I need to build a new registration system using my WebAssist software - and I'd like the same registration system to work with my PowerStore 3.

Should I set up the master user registration using this User Registration Solution Pack? Will it work with an existing database and SA1 encryption? Or should I just create a new one using Security Assist? OR - is it possible to adapt the PowerStore3 registration system to work with the existing database and use this for the entire site? And will this all work if these directories are in sub directories of my website. (It is like this website/wholesale/store
The wholesale directory is password protected and within a sub directory of my website, and the store being a PowerStore within the wholesale directory.)

I know that I need to upgrade my Universal Email and order the CSS Form builder. I have DataAssist, eCart5 and Security Assist as well. I'm just trying for ADDT type full integration with your products.

Thank you!