This is how i got PCI/PCIe passthough working in the below example i got a server grade PCIe BluecherryDVR capture card going with Proxmox 2.3. Also my original troubleshooting posts regarding this incredibly useful feature of KVM can be found here this details what you must do to find device settings and types. If i get time i will condense this onto this page but for now you can peruse threw the below posts and find what you need.
Add IOmmu support to the kernel i have included Intel support since that is normally what i use however complete instructions can be found at the Proxmox wiki http://pve.proxmox.com/wiki/Pci_passthrough
# update-grub # reboot
Then add the following to your /etc/pve/nodes/proxmox/qemu-server/XXX.conf