Sony VAIO VGC-RT1SU in Desktop PCs

All-in-one PCs always seem to be hamstrung by compromises. For all their effortless style - most of them do look stunning on a desk, after all - their reliance on mainly mobile parts means that performance is more akin to a laptop with a large screen, rather than a compact unit that can mix it with the best desktop systems.

The latest Sony VAIO - the hulking VGC-RT1SU - sets out to change all of this, with the highlights a desktop quad-core processor (Intel's 2.66GHz Core 2 Quad Q9400), a Blu-ray drive and massive 25.5in screen. The latter is of particular interest: it's the largest screen we've seen on an all-in-one by several inches, and comes complete with a huge native resolution of 1,900 x 1,200, comfortably enough for movie playback at a full 1080p.

This combination achieved impressive results in our 2D benchmarks, and a score at 1.6 is quicker than any other all-in-one we've seen. Other recent contenders, including the HP TouchSmart IQ500 (web ID: 222441), Dell XPS One (web ID: 181470) and Apple iMac (see p88) haven't been able to surpass 1.21. It's an impressive result and it's quiet, making it ideal for a machine that's being targeted as much at professional users as Blu-ray buffs.

The complement of RAM doesn't hurt here, with a healthy 4GB, while Nvidia's GeForce 9600M GT graphics chip - Sony's only concession to mobile computing - still manages a just about playable 22fps in our medium-quality Crysis benchmark, and 78fps in the low-quality test. Modern games, then, aren't beyond the Sony's reach. Meanwhile, a pair of 500GB Western Digital Caviar hard disks provide 919GB of formatted storage capacity, and the Blu-ray drive is one of the more versatile we've seen, capable of writing to single and dual-layer discs as well as reading them.

The star of the show is the screen: it's a superb panel. As well as its large size and high resolution our tests revealed crisp detail and generally good colour reproduction. There was a slight blue hue to some colours, however it wasn't too distracting and lent movies a somewhat grittier, realistic tone.

The 25.5in panel is encased within one of the most imposing all-in-one cases that we've seen. It's a far cry from the svelte red chassis of the Dell XPS One or glass surround of Sony VAIO LT2S (web ID: 183744). Instead, the sturdy black exterior looks more like a chunky TV than a PC, measuring a mighty 94mm thick and 661mm wide.

The right-hand side of the huge chassis harbours plenty of ports and helpful features: aside from the Blu-ray drive, there's a button to turn the screen off, a WLAN switch and a couple of USB ports, as well as a volume control. The left-hand side is just as well-appointed, with headphone and microphone jacks, another USB port, eSATA, mini-FireWire and a couple of card readers - one for smaller media, such as SD and MS, and a larger one for CompactFlash. There's a further two USB ports, an S/PDIF output, a Gigabit Ethernet socket and HDMI in and out sockets on the rear.

And the included peripherals offer more versatility than the usual Logitech or Microsoft fare. While the mouse is a basic, slightly angular model, the wireless keyboard is more impressive - a small trackpad and pair of mouse buttons to the right of the keys allow it to be used on the sofa.

But before you get your wallet out, this all bears a hefty price tag: £1,701 exc VAT to be precise. It's considerably more expensive than any of its rivals, with the Dell XPS One costing £850 and the most expensive 24in iMac costing £1,182. Even the TouchSmart IQ500, complete with touchscreen loveliness, costs only £936. And for all its high-brow specification, it also misses out one key feature - a TV tuner. It's a bizarre omission in such a clearly multimedia-focused machine.