I don't know, man...the Modern High Gain model in the V-Amp is a Soldano model and I have always found it to be HUGE. Perhaps you didn't tweak the V-Amp enough? When I evacuated for Katrina I was hanging out with this total death metal dude. I had my V-Amp Pro with me and we hooked it up through some little powered PC speakers. He went ballistic for the Modern High Gain model and was cranking out the Death Metal non stop with it!!! He promptly went out and bought himself one.
You need to try it with various cabinet models to get the tone you like. Also, you can double the gain on the V-Amp 2/Pro if you want, there is a mode for increasing the gain. You need to push #2 when in edit mode. You can choose 0, for regular gain, or 1 for double gain. I find the Modern High Gain sounds best through cabinets #10 (custom 2x12) #15, 4x12 and #12, vintage 4x12. It definitely needs some minor tweaking to find your desired tone. However, it has a killer Soldano sound, if you ask me.
I can't tell you the difference between the Soldano Model on the POD2 and the XT...I have only heard it on the POD2.
Mike