New Desktop - HP Z1 g2 or build a Origin ?

Hi Guys,

i currently have a Dell XPS 27 AiO 2012 which i love but want to update to something more powerful

has to be PC due to software and prefer not to use bootcamp but would love a macpro in someways. But have narrowed it down to a workstation HP Z1 gen 2 or Build a custom PC from Origin genesis or millenium. i want a powerful pc for a mix of software/graphic use and casual gaming etc... maybe the top spec origin is overkill but god its nice and eye water expensive

havn't really liked win8 before so currently use win 7 but im really hoping the new win8.1 coming update will be finally the right time to switch

thanks