I ran 6 of the heavy duty brocks clutch springs and the lever didn't seem bad at all for the street and held up to a lot of track abuse. I eventually went with 2 or 3 of cycle concepts super heavy duty springs with 3 or 4 of the brocks ones now and the lever definitely got a lot harder to pull and on a street bike in a lot of traffic I don't know if I would love it. I rode a buddys gen 4 with stock springs and thought his clutch was broken and felt weird as it pulled so soft it felt like I wasn't pulling anything.
I run the gen 1 clutch pack from cycle concepts currently and seems to be solid, always ran their gen 2-4 packs before but he stopped selling those. I've heard good things about KG clutches in the past if I remember right too.