OD1 Makes, sense - I think there was never a decent cab when I was around (Also, RIP TInus, sweet dude!).
I think a 6505 is a totally different beast - higher gain chuggage more than Bluesy rock goodness?. My mate has a older 5150 and ends up using a older Marshall Valvestate for blues & cleans rather than the 5150. But it get thunderous at jams, the 5150 & a 4x12 moves a lot of air. It even doubles as a bass amp when he pulls out the 8 string djent-stick
if you wanna compare the Kock to something Peavey, I reckon a Classic 30 would be the one to A/B it with.