Yes ... E15's and F21's. They are the cross-over engines from black powder to the wonderful world of AP! I would never trust my Saturn V to a D12-3 ... only an E15-4.
Are the E-15s back in production?
F40 and G64 reloads are cool. For SU, I like Econojets for "quick shots" and G80's since there's no comparable mid-power reload.