Try the Evesham micros website, chose the one nearest to what you require and then look through the options available to add on or substitute.( they even do overclocking if you want it). I can vouch for their after sales service, my video card started playing up after 10 months I rang them up, spoke to the help desk who talked me trough a couple of things which didn't clear the problems. The next day an engineer arrives changes the card, it was worse so he went back to his car and brought back a better spec one which is still going strong after 4 years, all for no charge.