I believe he is on 10 spd, not 11, so the 6800 stuff won't work. Even if that is true, IF he is on 6800, then 5800 105 cassettes and derailleurs would work the exact same for much less money. Cassettes are $35, Long Cage RDs are around $50. They work perfectly with Ultegra, and the only difference is cost and a few grams. Art's Cyclery did a whole writeup on this, and basically said go with 105 cassettes and DRs, Ultegra cranks and chain and BB (for stiffness and wear resistance), DA if you can afford it. The shifters are all the same, and go with DA cables as that makes the most differences.