Elixer string. I run them on my Martin OM21 and they last a long time. Yes, more expensive but they will sound good forever and feel smooth.
http://www.juststrings.com/elx-16027.html
100W 2-12 is overkill for almost every situation. I gigged for years with 22W 1-12 amps. Almost every guitard I play with is too loud and doesn't understand the basics. Here's my short list:
1. Don't play your music for your ankles. Either put the cabinet on a chair or angle it towards your head. Most people are way too loud because of this. Also, if you're sitting on your speaker you also can't hear how loud it is.
2. When playing in a band, re-eq your sound - mostly, cut the damn bass. A guitar tone that sounds great in the bedroom by yourself will likely sound like crap in a full band situation. The most common mistake is cranking up the low end to sound more "full". That's great, but it fights with the bass and kick drum and ends up making things like mud, leading to volume wars.
3. A low power tube amp cranked sounds infinitely better than a high power amp on 1. Guitars cut naturally - you don't need a ton of power to be heard. Oh, and wear ear protection when you play in a band situation.