Cross fit and what races for 2013

I don't have a lot time to run so crossfit is intriguing. I just started and one thing is for sure my pecks rarely hurt after a run and after crossfit my upper body is really sore. The best part about crossfit is it takes 20 minutes or so. Knowing I only have enough time to run 25 miles a week should I cross train with some crossfit. The other dilemma is what races to sign up for. I know I am not doing any 100s and I got the go ahead to do only 2 races. I want to do a 50 in Kansas, dirty thirty, quad rock, Leadville marathon, silver king, pace for Leadville (does not count as a race) and Urok 100k. Which ones?