I'm looking at a Magpul CTR stock to put on my A2 AR. I've swapped the upper for a flat top also, but I don't think that will make a difference in this.

I see mil-spec buffer tube assembly kits on ebay for $30-$40. They include a 6 position buffer tube, spring, buffer, and plate nut.

1. Is this all the hardware I will need for the conversion?
2. What would happen if a buffer malfunctioned? i.e. I bought a cheap one and it "messed up", not sure what would happen?

Should I spend a few extra bucks on a reputable brand or if it's made out of the same material is it pretty much the same? I'm not concerned about weight either.

spend the extra coin.

Do you think things on cheaperthandirt.com are okay or would you guys stay away from there? I've never ordered anything from them myself.

Also, are the parts I listed above all I'll need (including the stock) to complete the conversion? Thanks.

Yup.

Receiver extension, endplate, castle nut, buffer, spring.

ETA: Bravo Company, Rainier Arms, Brownells, Mid Way

Check out Damage Industries (they're an Industry Partner). I got a buffer tube assembly kit from them that was nice quality for a good price.

Is "milspec tube" or "buffer tube" the same part as "receiver extension"?

+1 on Damage Industries, I think I'm just going to order from them - thanks!

"Buffer tube" is a colloquialism for "receiver extension"

"Mil-spec" and "commercial" identify the external dimensions of the tubes. Make sure you have the right one for the stock you're using. They'll both fit the receiver threads, but won't fit the same stocks. Although, almost every collapsible stock can be bought in either size.

i usually use these delton stock kits  here a little over 80 bucks with the spring and buffer.

i recommend them. the're 7075T6.

im not promoting my store (mods dont get pissed, if anything im pointing the guy toward delton) im just saying i sell these and people are always happy with them. much better than the 39 dollar stuff you find.

Just another option here, I've always had great service from these guys. Scroll down and you'll see the CTR with a complete mil-spec kit with everything you need:

PK Firearms