Overall, mahogany will take away a lot of the sparkle and add some lower-end punch, as one of the earlier posters said. If you prefer punch over sparkle, then go for it... but if you prefer punch over sparkle, you may be better off selling your Strat to get an SG or something along those lines. There's a reason why alder/ash + maple is so popular with single coils - it brings out that high-end spanky sound, which is the single-coil specialty. If you're looking for a punchier sound, an alder body and single coil pickups will probably hold you back more than a maple neck.
Bottom line, if you want to keep your bell-high tones, a mahogany neck isn't your best bet - and if you want to add midrange/low-end punch, you'll probably benefit more from a mahogany (or rosewood) body than a mahogany neck.