What are realistic PC alternatives to a Mac Mini?

I'm looking to replace a recently deceased Vaio tower as a family room / home office PC, on pretty much 24/7 - what is there in a similar form factor that's quiet / silent and with similar amount of power but for less money? Or is the Mini a situation where Apple actually give you better value for money than buying a PC?

Given that its a fair way through its lifecycle, for about £450 I can pick up the 2.5 i5 Mini (the one with discreet graphics), the small, silent / quiet PCs in that price range are pretty much all HTPCs or nettops, neither of which would comfortably handle some of the stuff I'll throw their way (Creative Suite + very light video editing). The closest seems to be the Fujitsu Q900/910/9000, but thats a bit more expensive (though yes it comes with an optical drive), the ASRock CoreHT looks decent too. And before you start, no I'm not going to build my own machine, *fun* as that might be I've got nowhere near the time or skill to try that. All the PC building services I've looked at come in more expensive.

The Mini just seems like much better value than the competition, and would work well with what I want to do. So, what might be my Windows-based options? Realistically life would probably be easier staying PC...