AX8 with USB interface

[Smittefar]

I think it's just the way it is. I remember the old focusrite 2i2 had the same problem in that it would clip no matter what with a guitar even if you put the input gain all the way down. Probably just because they're the lower end models.

On the Focusrite (I don't know the Presonus), the problem with clipping was only with the Hi-Z input. You should be using line level inpus with AX8, so you will not have that problem.

 

[Barmaleus]

SPDIF does not always equal lower latency, in fact I believe it typically equals higher latency. I have a Maya card and SPDIF is subject to the the sound card latency settings which even at it's lowest is higher than direct monitoring of the analog inputs. Unless your soundcard taps the SPDIF signal and converts to analog prior to the sound card's latency settings, it will always introduce more latency. You do save an AD/DA for recording purposes, whether or not that makes a difference is debatable.

Fair point.
I'd say there will be no drastic difference anyway (in terms of spdif vs analog latency) with a mid-range sound card. Either connection will provide great results.