[ALUG] £400 - what's the best buy?

I want to get a new PC - what would be the best buy? I wondered about this one http://www.ebuyer.com/product/193626 Perhaps some of you build PCs in which case can you do better buy than this? Obviously to run linux [inc compiz which i haven't been able to do on current PC]. I had thought about a laptop but i thought they ran a bit slower than a desktop for a comparable spec. thanks james