okay, so i'm a messenger and i've built up a winter bike , a fixed gear mountain bike. the fixed gear is to eliminate the slip of brake pads on snowy rims. i know i'm going to run into those problems, since i won't have the option to avoid riding in snow at various points of the winter, so i'm also thinking that in addition, i should replace the front fork and wheel with disc brakes. i don't want to spend too much, since i just don't make that kind of scratch, but i also know i can't go too cheap. then again, even a cheap disc brake that will work more regularly is better than a rim brake that won't. either way...it's only been a few months since i started building this bike and learning more about mountain bikes that i really became more interested in mountain biking, so i don't know what all my options are yet. any suggestions?