I would say it's overpriced (price up the components yourself to see) plus:
You won't need a HD6850 unless you're gaming;
The motherboard will have to be swapped out at some stage unless it's the B3 revision with revised SATA 3 chipset;
4GB RAM should be sufficient;
I'd spec Windows 7 Home Premium unless you need XP mode that 'Professional' provides;
I'd do some research to find out who makes Xigmatech PSUs or consider a known quality brand.
This would have been better in Consumerwatch.