The Omni 27 Quad is HP's latest all-in-one that shares many aesthetic characteristics with the TouchSmart 520 we recently reviewed, despite being in a different class. Inside we find a third-generation Intel Core i5-3550S Ivy Bridge processor clocked at 3.0GHz, 8GB of DDR3 memory, a 2TB Hitachi hard drive spinning at 7,200 RPM, Radeon HD 6550A graphics and Beats Audio.

There's a 27-inch display tucked behind the edge-to-edge glass that admittedly looks much cleaner than what we saw on the 520. The difference here is that the Omni's 27-inch display isn't touch-sensitive, something a lot of people won't really miss in a pre-Windows 8 desktop system, or a desktop in general.

When Apple updated its notebook lineup earlier this month we were eager to find out how well the new MacBook Air stacked up next to a couple of Ultrabook alternatives. Turned out the so-called “Apple Tax” wasn’t as much of an issue as Apple detractors often claim.

Now we’re taking a look at another area of the PC market that’s experiencing healthy growth in recent times, comparing Apple’s 27-inch iMac to all-in-one alternatives from the likes of Dell, HP and newcomer Vizio. As we’ve said before, we don’t expect this comparison to be representative of the entire Apple Tax argument, but it will help paint a better picture as we contrast it with our previous findings.