Is the Alienware x51 desktop good for gaming?

No. It's a prebuilt gaming computer. You should build your own because it's more upgradeable and it would run cooler and quieter than the X51. You can use any monitor you want but DVI or Displayport is better than hdmi.

http://pcpartpicker.com/p/3p3k3

The alienware brand of computers are good computers, but they are overpriced for the components that are put into them. You are paying more for the name than anything. But on their website you have the option of paying more to add a keyboard and mouse. And No you can use any monitor for them as long as the computer and monitor have the same connectors.

Here's the deal with the X-51. It configurable when you buy it on Dell's website, so you can get decent enough components, good enough to run current games (and no you don't get a monitor, but any brand of monitor will work just fine- you want a monitor with a minimum of 1920x1080 resolution- and you can get one from Dell if you want when you configure the X-51).

My main problem is that the X-51 is essentially a closed system, and there really isn't any upgrading that you will be able to do to it. This is the greatest thing about gaming on a desktop PC, you can always upgrade your rig. But with an X-51 ---you can't. Its almost like having a laptop. I have a hard time with that one. Plus it has an incredibly weak PSU which is a special 330 watt proprietary Dell one, so you can't upgrade it or get a more powerful graphics card (A HUGE ISSUE FOR GAMERS)!

And I have to agree with the answer that recommend building your own. Its actually not hard at all, and anyone can do it. Plus you can pick exactly which components you want. Websites like PC PartPicker helps streamline the process, and all but eliminate incompatibility issues.

But back to the X-51---Looks like right now, the best possible graphics card you can get is the GTX 760 Ti (and this is actually a special slower OEM Dell version, not as good as say an MSI Gaming Edition 760 Ti), so in a year or so when you find this cards not quite cutting it, it'll be time to sell the whole system. With a regular desktop, you could just upgrade the card. You can get a i7 4770 with an X-51 which is a great CPU, but by the time you set up an X-51 with a good CPU, the 760 Ti, and a SSD+HDD you've spent over $1600. And you'll still need a monitor. Way Too much money.

http://pcpartpicker.com/

But I realize that some folks that could build choose not to, and want a pre-built. I just can't recommend the Alienware X-51. Too many bad points.

If you absolutely want a pre-built, I would look to Digital Storm, Origin, Falcon Northwest, Velocity Micro, or Maingear. There are all overpriced, but Alienware is the worst for overcharging.