We run K12's as mains and I have a CLR and I feel like they both sound good.
I"l have to say I did purchase some of the new packs from the cab factory via Andy. The bronze presets are killer. They sound freaking great through K12's. So 30 bux and you're off and running.
I do use the Lo and HI cut in the cab blocks. Some people go as high as 150 on the low and around 6000 on the high. You can't miss by going 100 and 7000 though. I played through a pod this weekend and I really felt the excessive digital highs and lows. If they had a similar page as "our" cab block, that would have been the first place I would have tried to tame those issues.
Tyler G has this mid bump PEQ he puts at the end of his chain that I"m currently using. It does help IMO. I cant' remember the settings but Yek had a post a while back that talks about tweaking with FRFR. Its in his post, i'm sure you can do a search and find it.
I try to have the speakers on stands when i'm dialing in tones so it will mimic what the audience will hear.
I run my CLR off of output two and tweak the global EQ for out 2 to compensate for it being on the floor. Sometimes it's too bassy. I usually drop the gain as well to about minus 4 or 5 db there.