Antec TX1050B Blk 20" ATX w/500W PS seems like a good option for the price. The PSU only comes with one PCI-E connector. The PSU is modular, so in the future if I went SLi could I purchase an additional PCI-E connector?
More aboutbuying additional connector modular
You can either purchase another 6 pin pci-e connector or just buy a dual 4 pin molex to single 6 pin adaptor (this will probably be cheaper).