Love the idea of a metal pack. Working with all my cab stuff that most of you know i have come to the conclusion, that for metal, the cab aspect is really more important than the amp side. Most modern high gain amps can produce very similar tones when cabs and mikes stay the same. So i personally would prefer less amps and more cab variations and combinations.
I bought the 6505 pack and love the lead tone. For my stuff that goes a little bit into the thrash direction, it sounds really awesome if you combine the 6505 with a bit of that classic Marshall G12T75 sound which have that special sawing high mids. So perhaps mixing cabs with different characters might be a really nice addition.