W/M with a stock n/a engine won't do much of anything at all. The water helps with cooling the intake charge, so does the methanol as well as increasing the octane rating which a stock Hemi really doesn't need. Being n/a, the w/m will displace some of your air and fuel which could actually hurt your performance where on a boosted application, it's being forced in until the valve slams shut. There is a positive side to adding a w/m kit to your stock n/a engine....I've heard of guy's installing one of those kits and besides adding w/m, they also added a couple oz of nitro methane to the mix and claimed they picked up another 30-40 hp according to their time slips.
I would use water/meth more to help with bringing down EGT's in a turbo setup (the water part) and so you could run more timing (the meth part). Id save the money on the water/meth, for the $300+ it would cost you to get a complete setup you could pick up a used nitrous setup if you don't already have it