Alienware's latest X51 gaming PC would not look out of place in an office.

Yes, it still has the brand's distinctive alien head logo on the front, but the company shows uncharacteristic restraint by putting just a couple of LED lights on the X51.

Also, unlike the huge desktop towers seen with gaming rigs, it is about the size of a game console. I like its svelte and compact design, though there is still room for improvement, like doing away with the unsightly external power brick.

The model reviewed here ($2,499) does not have an optical drive. Gamers probably won't miss this feature because PC games are widely available in digital game stores such as Steam and Origin.

If you need this feature, Alienware sells a lower-end model ($2,099) with a slot-loading optical drive.

But that model has a slower processor, lacks a solid-state drive and comes with a smaller 1TB hard drive. More importantly, it does not have the internal liquid-cooling feature of the more expensive version.

This liquid-cooling system lets Alienware overclock the X51's Intel Core i7 CPU to a higher frequency for a slight performance boost.

It is also the reason why the X51 can remain quiet while running a game, which is further helped by the use of a mid-range Nvidia GeForce GTX 960 graphics card that does not require a large and noisy cooling fan.

This graphics card is decent enough. For instance, with Crysis 3, it delivered an acceptable 40 frames per second (fps) at 1,920 by 1,080 pixels at the Very High setting. But it is unable to hit the 60fps required for a smooth, lag-free gaming experience.

There is an upgrade path, albeit a pricey one: Get the Alienware Graphics Amplifier and hook it up to the PC. This accessory supports a high-end graphics card (up to an Nvidia GeForce GTX 980 or an AMD Radeon R9 290X), which is used to improve the graphics performance of the connected X51.

The amplifier itself does not come with a graphics card. Since the X51 already has a mid-range GTX 960 card, it only makes sense to get a high-end card like the GeForce GTX 980.

This is where it gets pricey: the amplifier costs $419 while a GTX 980 graphics card is around $800. In other words, you are probably better off just getting a more powerful gaming PC from the start.

But the amplifier also works with Alienware's latest laptops. So the accessory may be worth the extra cost if you are thinking of buying an Alienware gaming laptop too.

Since it is a modern desktop PC, the X51 comes with two new USB 3.1 ports that support up to twice the transfer speed of the older 3.0 standard.

As usual, Alienware has preloaded the X51 with its proprietary apps, which lets you adjust settings, from the colour of the LEDs to the speed of the cooling fans.

• Compact liquid-cooled gaming PC performs decently in games. Just don't expect it to set any performance records.