The Astros farm system was recently ranked #10 in Baseball

10) Houston Astros (25 last year, ranked 11th on January 28th 2013, moved up to 10th on February 5th following Jed Lowrie trade): Another system that has improved rapidly. Strengths: 2012 draft class looks excellent thanks to inventive exploitation of new draft rules. Trades have dramatically improved system depth. Potential impact bats in Singleton, Correa, Springer. Weaknesses: pitching is weaker than hitting especially at the higher levels, no obvious rotation anchor types are close to the majors. It will take time for recent draftees to filter through system.

http://www.minorleagueball.com/2013/1/28/3925786/2013-baseball-farm-system-rankings