I use an AMT Pangaea, I tried the HD without cabs and into an IR loader on my laptop, sound is way better so I got the Pangaea!
I put in an amp block, disable the cab, put the effects loop block after the amp, Pangaea in the loop, job done!
I have the loop set to line level (switch on back of HD) and the pangaea set to that as well, it handles it fine, however the EPSi needs a much lower level, you need to set it to stomp and lower the send level on the effects loop and raise the return by the same amount...