Maintaining a geared bike really isn't hard. It's really just cable tension (limit screws shouldn't need to be touched after initial setup) and maybe once a year replacing cables and housing. Cleaning is easy enough, and gets stupid easy if you have a compressor. But if you don't want a geared bike that's fine.

A good set of pads will do more and be more cost effective than an all new caliper up front. I've never had a problem with my Tektro's when I was running single speed. You will get a bit of a performance jump going to something more expensive, but honestly I think the biggest price factor is weight. To cut significant weight and keep the performance is expensive. For some bargains look for 7600 series Durace or couple year old 105. Both will work great and be relatively light. Levers are kinda the same way. If you really skimp they'll feel mushy, but spend at least $40 on the pair and you should be fine. I use Cane Creek SCR5's and don't have any complaints. Oh and I live in Breckenridge. I deal with hills and **** weather often.