Um just use the Quattro, but your better off getting a gtx 5xx or 6xx!
I think the GTX 660ti would be a great card, faster and cheap and easy to find.
http://www.videocardbenchmark.net/high_end_gpus.html
Your quadro 4000 has TDP of 142W and one 6-pin power connector. The GTX 660ti has two 6-pin connectors and TDP of 150W. As long as you don't buy any overclocked or supercharged version of 660ti, you could be fine within the 300W limit (75w x 2 from two auxiliary power ports and 75W x 2 from PCIe slot). However you need a special cable connector like this to deal with the extra 6-pin connector on the GTX 660ti and split one auxiliary power source between the two video cards (use another cable to the other 6-pin connector). Or you could get a GTX 660 which has only one 6-pin connector and 140W TDP, and save all the troubles.Would I be able to still have the quadro 4000 in combination with the GTX 660ti? I need the quadro4k for work.