nutto: This information as of today is still pretty much undefined.
They did tests for such materials in foods years ago, and yes some companies did contain such ingredients.
Since then supposidly pet food companies have taken road kill and such out, but who knows if they really have. A lot of companies, including the ones you listed use non human grade "meat" and by meat I'm not necissarily talking about muscle, but other parts of an animals body.
I assume that since you've mentioned this, you've seen all the pages online, so theirs no reason for me to post them.
There are some food threads here where we have dicussed simple matters of cat foods, which should make it easy for you to pick a good one out. If you have any questions at all feel free to ask.
If you do a search for the brand names of the foods I list for you, you can find their official website, and ofton on there they will have a search function where you can find one of their retail stores near you.
PS: You could also consider feeding the RAW/BARF which is the best IMO.
I will also have my comparison charts of all cat food wet/dry. It's a very large task but I hope to have it completed soon, and I will make this availible online for everyone to reference.
Dry Cat Food:
Chicken Soup for the Pet Lovers Soul*
Canned/Wet Cat Food:
Felidea - Chicken & Lamb Forumla, Chicken & Rice
Wysong - Duck, Rabbit, Venison, Chicken, Beef
Pinnacle - Chicken & Tuna, Ocean Fish, Chicken & Ocean Fish
Wellness - Chicken & Hearing, Turkey & Salmon
Natural Balance - Ocean Fish, Ultra
Evolve - Chicken, Turkey