I have an HP elite 8300 cmt (mid tower case) that uses a single 4 pin connector (not common 24 pin)to supply power to the motherboard. The stock psu is rated about 320 watts. I would like to upgrade to about 600/800 watts to use new generation of gpu using about 120 to 180 watts tdp. So I need a new psu with the 4 pin connector for the motherboard with at least a single 6/8pin connector for gpu card. The physical size ot the stock hp psu may be slightly different than the common 24 pin psu. Does anyone know who sells this?