Need help with carpet search

I now hate looking for carpet more than shopping for a new car. OMG. I have been to five different stores this week and heard so many different things. So...I have some questions I hope some of you can answer.
1. Is 6.6 nylon really that much better than anso 6 nylon? I am trying to decide if Shaw anso nylon is just as good as stainmaster active family.
2. I want a carpet that has enough density that I can't feel the backing easily when I put my fingers in. I have samples that are 2400 density and 53 oz face weight from Shaw that are supposed to be "top of the line" and I can easily feel the backing. What kind of density will I need to avoid that?
3. I know that warranties require steam cleaning at least every 18 months. I have been told that with either r2x or stainmaster protectants that after three cleanings, all the protectant will essentially be gone. The warranties also state something like you can't put any foreign agents on the carpet. So does that mean you can't have scotchgard sprayed on when you get the steam cleaning done??

I have never been so frustrated with finding the specs on carpet. This forum and other sites have already been so helpful, but I still don't feel ready to make any kind of decision. I am looking at 1500 sq ft so this is going to be a lot of money for me. Any help would be appreciated.

 

Thanks. I think I have decided on a tuftex carpet that is part of the Stainmaster active family line. It is made of Luxerell BCF nylon. I believe I am correct that it is 6.6 nylon and obviously has stainmaster protection. It has a density of 3063, pile height of .63, 7.7 twist and face weight of 54 oz, so I am hoping this will be durable enough. Running 5.19 sq ft installed.

One last question. The carpet dealer only offers one option for pad- a Spillgard 1/2 inch 8 lb pad. Is it possible 1/2 inch is too thick or should it be OK?