Check out Sager's. If you like the flashiness of an Alienware then you won't find it there though, the laptops look like nothing more than a laptop. They are better priced for what you get though and can get a much better laptop in the same size w/ a Sager. Best gaming notebooks as far as I'm concerned and it's what I'll be getting (as soon as Ivy Bridge is released). The next models will have backlit keyboards and optimus. http://www.xoticpc.com/ sales them http://malibal.com/ also sales them but w/ out Sager branding so they are a bit cheaper. The Lotus P150HM at Malibal is the same as the NP8150 at Xotic. Also check out http://forum.notebookreview.com/ for any of the questions, they can help you out over there for any of the laptops
It's better to look at the individual specs rather than the companies on a standalone basis. Alienware is a little more flashy with the alien lights and what not. ASUS also makes a quality gaming rig, but not as cool looking - probably cheaper though. If you can get a good deal on a gen2 Core i7-based (Sandy Bridge) system, then go for it. Although, if you're a gamer you might be interested in an Ivy Bridge-based system (April launch) since its 22nm (lower power) and chipset has full DX11 support. Probably not a huge deal since you'll be using a discrete graphics cards though. Never heard of Sager's.
I have one. Build quality is pretty good. The only thing I can really complain about are the really substandard speakers installed, but for me, it's not really a problem. Like the poster above said, you can get the same components (if not better) on a Sager for a lot cheaper than an Alienware.
My friend says he owns one and 3D capable. He said he's so happy with it. He spent 2K though. If you have the money go for it.