Crossfire + Onboard for second monitor.
So I have two HD 7870 running in crossfire-mode, which means only the primary card can be plugged into a monitor. I have 2 monitors, which are both VGA. I have 2 VGA-to-DVI converters, but sadly the 7870 only has 1 DVI and the rest are displayport and hdmi. I can turn on my onboard Intel HD and plug in my second monitor, but I was wondering if there are any performance drawbacks I might run into? The reason I'm doing this is mainly to avoid having to buy an adapter.