I too was shocked that you started with Newport! As you've probably discovered by now, it's more of an endurance workout and intended to be used with a lighter kettlebell. Anthony suggests that women start with an 8kg bell. Keith Weber's "extreme kettlebell" dvd is also an endurance workout and you should use a lighter kb for it. It reminds me in rate, pace, and intensity of AoS Newport.
Providence is a strength building workout and you can go a bit heavier in that one, of course picking the right size kettlebell for the exercise. However, if a 20lber is all that you have, work with it
Firepower is right in the middle, kind of combining strength, endurance, and introducing some double KB work. Santa Monica is a jack of all trades, kick butt, AoS workout that you will love.
If you're looking for something catered specifically towards beginners, I suggest the AoS Clinic DVD or Sarah Lurie's DVDs. Lauren Brooks/Lisa Shaffer have a combo DVD that is also quite good. You'll find alot of great DVDs on the market, but alot of crap is out there too. Ask around for opinions and choose based upon your skill level. From Russia with Tough Love or Enter the Kettlebell are also great for those getting started with kettlebell training.
Let me know if you have any KB questions. I've been training with them since 2005 and an avid follower of the best in the industry. I'm very happy to see them growing in popularity over here in Cathe-land.
Good luck!