Apple's new 27-inch iMac can be described in one word: stunning.

Don't take my word for it. That's based on the cluster of graphic designers and techie-types who popped into my office last week to get a gander at the newest all-in-one Mac from Apple. Part of it might have been the novelty: Apple unveiled these larger, widescreen iMacs on Oct 20 and sent one over for review purposes two days later. It's the biggest change for the iMac since it went aluminum-and-black in late 2007.

Yes, it comes with more processing power and the sleek new Magic Mouse, which several people tried out to mixed reviews. (I love it; others found it a little heavy.) But mostly, it was the super-high-resolution screen that drew people in.

That screen, the largest LED-backlit computer display out there for now, offers a resolution of 2,560x1,440 pixels for a true 16x9 aspect ratio. That's 90% of the screen real estate you'd get from Apple's gargantuan 30-inch Cinema Display and it's perfect for viewing high-definition (HD) content. Judging from the coos of approval I heard when I fired up some HD movie trailers for the huddled masses, this iMac should sell well.

In fact, HD content is so sharp and bright that it almost looks 3D. The big question you'll be asking yourself is: "Do I put this in an office or show it off in the living room?" (I'm having that exact discussion right now with my partner.)

According to Apple, the basic model offers 17 per cent more pixels than the old 20-inch iterations. The main difference between the two is the size of the hard drive and the graphics cards. The base iMac comes with a 1TB drive, offering twice the capacity of the basic model, and uses the ATI Radeon HD 4670 video card with 256MB of video RAM. You can also get it with the now-ubiquitous Nvidia GeForce 9400M card, which relies on 256MB of shared system memory and is used in a number of Apple products.

The model I reviewed is not even the high-end iMac. That title goes to a version wiyh a quad-core Intel Core i5 processor, which won't be shipping until next month.

All of the iMacs (except the top model) come with a 3.06GHz Core 2 Duo chip and 4GB of RAM. But Apple has added two more RAM slots, making it easy (though not necessarily cheaper) to max out the memory.

For most users, 4GB should be plenty. But if you do decide to add more RAM, you can double it in the smaller iMacs to 8GB, and quadruple it in the 27-inch models to 16GB. You can also boost the processor from 3.06GHz to 3.33GHz.

If the Core i5 isn't enough power for you, there's an optional 2.8-GHz Core i7. That, combined with the super-size screen, should offer a powerful punch for creatives used to Apple's Mac Pros.

According to Apple, both of the Core chips can run at faster frequencies if all of their cores aren't being taxed at 100%. With Intel's Turbo Boost technology, the 2.66GHz chip can go up to 3.2GHz and the faster 2.8GHz processor can zip up to 3.46GHz. In addition, it supports Hyper-Threading, allowing the Mac OS X 10.6 Snow Leopard to take advantage of all four cores. Both of the Core processors also have 8MB of Level 3 cache memory and an integrated memory controller, which helps them churn through data even faster.

Apple says the Core i5 processor is about twice as fast as the 3.06-GHz processor in the old top-end iMac, and the Core i5 is 2.4 times faster.

More high-end tweaks

In addition to opting for a faster processor and more RAM, you can also max out the hard drive with a 2TB model. That's going to be useful if you decide to use your iMac for large creative projects. Given the limited upgrade options for the iMac, it pays to assess your needs wisely and choose accordingly when you buy. No doubt, 2TB sounds like a lot of growing room now, but will it feel that way in three years?

On the 27-in. model I'm using, you can move from the ATI Radeon HD 4670 graphics card with 256MB of video RAM to an ATI Radeon HD 4850, which doubles the video RAM and offers an 80% performance boost. If you play with 3D objects or use 3D accelerated tools within video editing suites (or even Photoshop), take note