I have rockcrushers on my D44s, they are far from weak. They have taken quite a few blows, and show no wear.
Rockcrusher got bought out/sold/whatever (it was a big legal mess) a while ago, and I beleive they are now known as Solid. The covers never were expensive, I beleive I got mine for like less than 100 each.
For 65 bucks it's well worth, buy it.