Check out this aofroobs post, may be what you are after: http://aofroobs.com/viewtopic.php?f=20&t=735
Gets 200 imps in 2 “steps” on a level 100 soldier.
Edit: Just reread your post and this isn’t quite what you’re after. I’ll throw in my view though: after 125 imps at level 60 I normally throw on 150s at level 90 and approx 185s about level 120 if I don’t feel like stretching to ql 200s