I am thinking about getting a AR-Lower to SBR , but so many company who mark AR it hard for me to pick ,  also I will be use with different cal such as 7.62x25 and 5.45x39. any info will help

AGP.  Very nice and a great price.  Service is excellent.

Any lower will answer.

Pretty much any lower will work. I went with an lmt defender lower that I added a sopmod stock to. Next one will be a bcm one to match a bcm upper, a larue stripped lower, or a kac complete lower. The kac lower is expensive but when you look at everything it comes with it isn't badly priced.

I used a LMT Defender Lower, if i could do it again i would go KAC IWS

I consider going through the trouble of SBRing a lower to be something on the special side.  Although opinions may differ, I think that one lower is as good as another, as long as it is mil spec.  I like the Spike's lowers for one reason.  I really like the color filled roll mark.  I just picked one up from a local dealer with the color filled spider on the side, marked "Multi Cal" and it has the full auto position roll marked and color filled as well.  This is the one that I'm going to SBR.  I just think it looks cool.  I'm just not sure of what's going on with the prices on Spike's site.  I got mine for $125, Spike's wants $180 and up for them.

I took the factory route and purchased 2 Colt 6921's from Clyde Armory.

Once you have them, it doesn't really matter what round you shoot out of it. Now that Colt has a completely standard lower, it's one of the best ways to go.

You can also get a factory LMT SBR from Clyde's as well.

Clyde's SBR page

Couple of ways to go here. For the most part, all forged lowers (that are properly milled in spec) are fine so the difference really comes down to the details and personal preference. Whatever lower you go with, make sure you buy, build and use it for a while before sending out the $200 tax fee. It would really suck to do that only to find your new lower is out of spec. Also keep in mind that once you SBR a lower, it's pretty much yours until you die unless you decide to waste the $200 tax stamp and have it removed from the registry. SO that being the case, I wouldn't just use the first cheap lower I found.

Here are some options...

S&W lowers - one of the only lowers that have no caliber markings at all. Good choice for a build that may see many different options.
Mega Lowers - I've had a lot of lowers from a lot of different sources but hands down, the Mega lowers are the nicest machined lowers I've seen. They are marked Cal = Multiple which is also a good way to handle a lower that will see multiple uppers.

Of go with a lower that matches the intended upper. It doesn't matter in the least but I still like my lowers to match my uppers when possible so if I knew I was going with LMT's 10.5" upper, I would use one of their lowers

Like the others, make sure you get a quality lower before the time and money starts being invested to SBR it. My first was a dedicated magwell 9mm and the next is a Black Rain Ordnance. No different than a forged one, but if I'm gonna drop the $200, I want something cool and not one that looks like the next guys. Your choice, but thats the way I see it.