The extra queue pairs in the Intel® 82576 Gigabit Ethernet Controller were never supported by any software and drivers. So both the Intel® Ethernet Controller I350 and the Intel® 82576 Gigabit Ethernet Controller support up to 8 virtual machine queues per port.
If you are going to buy quad port adapters, a quick comparison of the Intel® Gigabit ET2 Quad Port Server Adapter and the Intel® Ethernet Server Adapter I350-T4 shows the latter to be the best choice with an edge in power efficiency and a faster PCIe bus rate. If you need IPSec offload capability in a gigabit adapter then you would need the older Intel® Gigabit ET2 Quad Port Server Adapter.
If you are running a lot of virtual machines on one server, you might want to consider a 10-gigabit adapter like the Intel Ethernet Converged Network Adapter X540-T2. The adapter can be used in a gigabit network and will be ready for an infrastructure upgrade to 10-gigabit. As a bonus you will have 63 queues per port for virtual machine queues or for SR-IOV.