Khagan or other 4 star reds

Hi empire brains…

I have boldtusk at 4.1 and wondering about his other red partner…

I can ascend khagan from 2.60 to level 3.1 and then 3.70. (i love his versatility. More then i live collen for example)

Or i can use the blades and take some of my 4 Stars way all the Way up. I have collen gormek scarlet keily at about 2.12 and can use the blades and feeders for them

Or leave khagan. Acsend them to 3 tier and wait for another red to pop and give him the blades

Any suggestions?

Boldtusk and Gormek synergize very well, so I would recommend leveling them first.