You might also want to consider a Logidy Epsi, it will allow you to load IRs and it's stereo(I just go mono-I think Torpedo is stereo) and it's cheaper, about $200 new.
I, like many others, was hating my tone and all the work and tweaking... and was ready to sell my HD500; until I used the Epsi. As many agree, the cabs seem to be the weak point. Once I had the Epsi, it was so much easier to dial in what I wanted. No fizz, no weird, loose bottom end.
I have the Epsi in my effects loop, that way all my outputs on the HD500 have the IRs. I go through an Alto ts112 and have one xlr from the HD500 go to the house.
I did a few clips a while back, maybe it might help.
This was my original patch before I got the Epsi
https://soundcloud.com/alphadog808/original-jcm800-patchno-epsi
Then the patch with the cabs off and Epsi on
https://soundcloud.com/alphadog808/jcm800-patch-with-epsi-on
Then I took another forum member's patch and this is his original, no Epsi
https://soundcloud.com/alphadog808/joel-no-epsi
Then I removed his cabs and added the Epsi
https://soundcloud.com/alphadog808/joel-epsi
Note, it's not really the Epsi that makes the difference, it's the IRs that do. I was using Ownhammer ones, but I can't remember which one. Hope it helps.
Oh, and I think one potential downside of the Epsi is that you won't be able to change cab IRs per patch. It's more of a choose one IR and roll with it. Doesn't bother me, but some users want one IR for clean, then one for lead, etc. I think the torpedo will allow you to change IRs on the fly.