So many 122mm guns, which is best for IS3

ARGO: I am currently working on my IS3 and I already have 2 of the 122mm guns but here i see this 122 BL9 gun and I wonder, is it worth the effort and 40+ thousand exp to get it. Will this gun be for my IS3 what the 107mm was for my KV3? In short, Does this gun have serious BOOM BOOM?