pcie 1.1 and 2.0 will run in either slot. the only difference in the 2 is that PCI e has the power pins on hte card giving the higher wattage.
pcie 16x is rated at 75 watts
pcie 2.0 16x is rated above 75 around 105 and up. which is why they have the power connectors on the card. either way you wont lost any performance as long as the card has its power.