The vast majority of aftermarket AR quad rails are going to be aluminum. As far as what brand.... that one is a can of worms! Everyone has their own preference on brands and it will probably come down to how much you want to spend and what you think looks the best.
Personally, I like the Yankee Hill Machine Diamond series quad rails, (www.yhm.net
) they are pretty reasonably priced and the top rail extends over the supplied jam nut to make a seamless rail from your upper to the quad rail.
If you want to spend about $100 more take a look at Seekins Precision (www.seekinsprecision.com
) their BAR rail is pretty bad ass.
Good luck to you and post some pics when you get the new furniture in!