Bit-Tech published a review of Nesteq's Nova 600W External PSU
It's a great looking and innovative product with so much potential, that actually works silently rather than just claiming it on the packaging like so many others. But unfortunately there was a complete lacking in attention to detail: the PSU fails on half of its rails as soon as you hit full load and the cabling quality and connectors used are nothing special.Nesteq Nova 600W External PSU Review
At £130 including VAT, it is a lot of money to spend and if you're using it for a little case with reasonably low power components for a silent system, you'll likely get away with it. 3.3V and 5V are less important that 12V rails in a modern PC, but you're more likely to encounter stability issues if you use it with a higher specced PC.