Since you mentioned 2nd Gen Core CPUs, you need the Centrino series card that were released at the same time as the 2nd Gen Core CPU's release date in order to be fully compatible with the chipset and WiDi.
So here are the only 2 Centrino cards for 2nd Gen CPUs that should have no issues getting WiDi to work:
Intel 6230 (dual band + Bluetooth): Amazon.com: Intel Centrino Advanced-N 6230 Wifi Half Mini Wireless Plug-In Card Data Transfer Rate 300 Bps: Computers & Accessories
Intel 6200 (dual band without Bluetooth): Amazon.com: Intel 6200 IEEE 802.11n (draft) Wi-Fi Adapter - Mini PCI Express - 300Mbps: Electronics
Do not get the 6205, 6235 or 7260 since those cards are for 3rd Gen and 4th Gen chipsets respectively. If you get these cards, there's a chance that they won't work or that WiDi won't work.