Hello Fabrice,
Thank you for taking an interest in our PCIe line of DAQ cards. I've taken a look at the USB-6211-OEM and the PCIe-6321 to see if they are similar in specifications and capabilities. I would say that the 6321 is a good match to replace your current USB card. As long as you intend to not use more I/O lines than intended or exceed the designated sampling speed then it should be a good replacement.
If you need high-speed sampling or more I/O lines for various tasks then another card may better suit your needs.
The resource below compares several of our X Series devices (USB and PCIe).
What is NI X Series? - 1. Product Overview
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These links may also prove helpful during your upgrade:
Major Differences Between E Series, M Series, and X Series NI DAQ Devices
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NI X Series Upgrade Guide (from USB to USB devices however)
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Regards,
Alex C.
