Does your bow need silencers to quiet it enough for hunting? If the answer is YES, then install the silencers. If you gotta have 'em, you gotta have 'em. No sense obsessing about speed loss when you're talking about a necessary accessory.

I'm no fan of leeches. I can't see spending that much money for something I'd have to have a chronograph and decibel meter to see any advantage over catwhiskers.