According to CCRL [1], Komodo 6 and Stockfish 4 are 20-25 Elo weaker than Houdini 3 (in the last few years Rybka wasn't able to compete with Houdini, in TCEC it wasn't even able to qualify into Stage 4). However TCEC uses development versions of Komodo and Stockfish that are much stronger than their latest stable releases.