I just got the O2+ODAC. I could not resist the price and hype.
First, I was expecting something bigger. It's so small. Yet, it has a big sound. It really sounds like a desktop amp.
Second, I was expecting bright and lean. But it's smooth, clean and not lean at all. Nice bass. Not something you get for something that resembles a portable amp. Really pleasantly surprised.
I tried my JH13pro. Wow. Nice and smooth. Not edgy or hot like I expected. The bass finally came alive, something that only happens with a good desktop amp on these.
I tried the Grado Magnums. It of course did not warm it up but it did it accentuate it. It sounded smooth.
I tried last my LCD-2 r.1. It no longer sounded warm and creamy. It sounded very neutral for the first time. At least to me.
But overall. I am very pleasantly happy. I could not ask for more for such a low price and size. Very powerful transportable, amp/dac combo that more than satisfies.
your magnums necessitate limba cups.