not much and it is grainy only in a way it is not gonna be as smooth as more expensive stuff!
I have not tried them headphones and this emphasis little bass so it will be even tighter and more controlled with this! I think this is a good option unless it requires a lot of power, i am not to aware of this model!
No, they don't require a lot of power. They're 2x35 ohms and can be driven by pretty much any source. So it looks like a good match indeed.
Here's a long appreciation thread on them if you're interested.