I've run a 1.5-5 Leupy, a 2.5-8 Leupy and now have a 1.5-6 Kahles with illuminated reticle on my 375H&H.
When it had the 1.5-5 on it I shot a blacktail at a lasered 384 yards. With the 1.5-6 I shot a widebeest at around 350 yards. What the hell you would need more magnification for I don't know.
If you want it, go for it but my feeling is if you can't hit something with 5-6 power 18X isn't going to help unless you are shooting squirrels at long range????????????

I am continually astounded at how quickly people make up their minds on little evidence or none at all.
Jack O'Connor