[nst7]

You can not use 2 different interfaces with Protools. It's either one or the other.

However, if your Saffire has a Spidf Digital input, then you can use the UX2, and Pod Farm, in standalone mode and use its Digital Spidf out into the Saffire.

So in this case the Saffire would be the Protools interface, then you'd launch the UX2 into standalone operation (along with Pod Farm-not as a plugin, but standalone), and then you could record your guitar sounds that way. There are setup guides in the manuals for this.