

You don’t need cards to have full bandwidth, they only time it will matter is when you’re loading the models on the card. You need a motherboard with x16 slots but even x4 connections would be good enough. Running the model doesn’t need a lot of bandwidth. Remember you only load the model once then reuse it.
An x4 pcie gen 4 slot has ~7.8 GiB/s theoretical transfer rate (after overhead), a x16 has ~31.5GiB/s - so disk I/O is likely your limit even for a x4 slot.
- overhead was already in calculations
Check with your provider for SIP server, username and password, and if they have a suggested app (even if you don’t want to use it, it means they have some kind of support). It’s probably in their support pages somewhere.