Thank you for your patience. It appears that your free slots are the PCI, PCIe x16 and PCIe x1.
Based on a huge number of positive reviews and better specifications as documented by the LAN card manufacturer, your best LAN card option for heavy gaming use is "Intel Gigabit CT PCI-E Network Adapter".
Here is the link from Amazon:
If you prefer to have dual LAN part, this is recommended for gaming computers:
I hope that helped.
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