I love the Lyr2. It is very versatile if you buy the version with both the SS and Tubes. It can power pretty much any full sized headphone, and it sounds even better when you have a decent DAC. The best thing about it is if you don't like the synergy with the stock tubes, you can always try your headphones with a variety of other tubes.
I personally really like the sound of the r70x and the Lyr2. I think the Lyr2 does a great job at providing the power to really make the r70x shine. I might also be a bit biased though because I think the r70x is the best headphone at its price point. I've tried the Lyr2 with the Phillips X2, K7xx, 99 classics (don't really need an amp like the Lyr2 though), and I greatly prefer the sound of the r70x.
Hope that helps.