I'm in the process of beefing up my venerable octacore 3,1 - and one of the items on the agenda is to upgrade the old nVidia 8800GT card that's in it. I've put an EVGA GTX670 card in which is now using both of the PCIe power sockets, but given that it's a 670 I have the usual black screen during the boot process. I've flashed what is supposedly a UEFI firmware to the card which I got from EVGA tech support, but I can't see that it made any difference. Now, should I be so inclined, what is the procedure if I were to put either the 8800GT in as well with external power, or something like a GT120 which doesn't need additional power - I would get the bootscreen during the process if the monitor is plugged into the 8800GT or GT120, but if I were to run something GPU heavy, such as (heaven forbid) a game, will it know to use the GTX670 for rendering and the weaker card just for output, or am I going to be causing a massive bottleneck? Any recommendations? So far the system is up to 32GB RAM, 2 2.8Ghz CPUs, 802.11n wireless, Bluetooth 4.0, SSD boot drive, and USB 3.0 support, so it seems a shame not to beef up the graphics as well to get a couple more years out of the trusty cheese grater.