Thats not PCIe x1, thats PCI (old slot), this is not suitable for your mainboard, as it doesn't have PCI. You may use semthing like that :
http://img.notebooksbilliger.de/ima...bit_CT_Desktop_Adapter_Bulk_EXPI9301CTBLK.jpg
But you have to check the compatibility to Proxmox first..
These works flawlessly with proxmox.
From my SuperMicro board (onboard though, but same chipset):
01:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
Subsystem: Super Micro Computer Inc Device 10d3
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx+
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
--
Capabilities: [140 v1] Device Serial Number 00-25-90-ff-ff-ae-e9-ac
Kernel driver in use: e1000e
ethtool -i eth1
driver: e1000e
version: 3.1.0.2-NAPI
firmware-version: 2.1-3
bus-info: 0000:02:00.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no