Good advice from Guinness as always. Madcow's site explains it in more detail, but basically the idea is that the goal is to get stronger, and to take the most direct route to that goal. It might be fun to periodize your training, but I really doubt it's optimal at this point; you almost certainly have a lot of room for progress on your dead and squat.
Do what allows you to make the fastest gains, which at this point is probably the SF 5x5. Believe me, if Guinness, blut wump or any of the other "veterans" on the board could still add 10 pounds to their squats twice a week as on the Rippetoe beginner program, that's what they'd be doing.