"I don't know...
I just ordered a DI V3 (with TCXO) and hooked it up. I just use the coax input on the DI, no usb connection, so I thought the firmware version was irrelevant.
I repeat: this thing sounds fantastic!"
I'm currently using a V1 with the TCXO upgrade powering it from a battery while using the coax input. I like it but wonder if the V3 is better even though it doesn't have up-sampling capabilities.