In that case, Armalite is a fine brand, well-built, good finish and lifetime warranty.
Currently, there are a lot of manufacturers that make really good, high quality ARs - and they include Armalite, Bushmaster, Colt, CMMG, RRA, and lots others. There really aren't huge differences between them, although some poeple really like some over others.
If you are asking for advice, I'd suggest a "flat-top" version (either rifle or carbine), instead of the one with the built-in carry handle you are a looking at. With a flat-top, you can still add a detachable carry handle, but it allows you a lot more options and flexibility for optics later if/when you decide on it.
Like this:
www.armalite.com/sales/catalog/rifles/m15a4_carbine.htm (obviously, you'd buy the scope or carry handle seperately).
Another really good option is a Rock River Arms (RRA) mid-length carbine with the flat-top. A lot of people like those, and in my opinion, it's the best "starter" configuration, with the best all-round flexibility.