I have been to 6 carpet stores in 2 days and have looked on-line...

but I can't find any carpet that matches the stats I need/want. Looking online I found that I need a twist of 4 or better, a face weight of 30 oz or better and a density of 3,000 or better. I also know I want BCF Nylon because it wears better and won't shed or fuzz up. Also, I'm not looking to spend a whole lot of money on this....any help from someone who knows about carpet would be a benefit. What is most important for me to look for out of the stats I have listed? I've also found a lot of the carpet stores don't know the stats for twist, density and face weight and they have to call the manufacturer or look it up online. I'm also getting varying estimates for the square yardage I will need...from 31 to 48...any ideas why some are telling me I will need 31 while others are telling me 48? Please help!