I have an XTLive that i was using with an Atomic Amp. Since my Atomic gave up the ghost, I've been plugging it in to the FX Return of the DT25 I have. I use the whole patches, including Amp models and setting the DT25 to Topology1, but it certainly works to disable the Amp model in the XTLive and just use FX. I have my HD500 hooked up too...
I have a Voodoo Labs Amp Selector, so I can run either,or,both. I'm also still using the Atomic cab as a second extension.
I love some of the Amp Models in my XTLive as much as any in the HD500...