Should sound great. Both of those sound badass in Marshall cabs.
I've got x patterns in both my Marshall cabs.
V30's x T75's in the 1960A and WGS BL80's x ET-65's in the VM 425A.
Yeah I got x in my 1960B and I really don't get why people think the marshall's are garbage. I love mine! How does the 80/65 cab compare to the 30/75? What are the differences?
The 80/65 cab is darker with less of that high end sizzle that you get with the T75's. The mids from the 65's are focused more in the middle spectrum, where the V30 are in the upper. I like the BL80 when mixing because they stay clear and have a massive tight lowend. The 75's handle the lows great too but they tend to color the sound more.
I actually just stumbled on the 80/65 mix one day while swapping speakers. I figured since they are both the same efficiency and their freq's seemed to compliment each other on paper so I tried it out.
I'm glad I did because the cab just grinds with sawtooth mids and the lows pound with precision.
Not taking anything away from the 30/75 mix though. That cab is killer and I often use it over my Mesa 4x12.