How does changstar look at Philips fidelio x2 compared to HD650??

X2 is a good choice among mid-fi purgatory. HD650 is at least a class over mid-fi. Depending upon person HD650 may be considered end-game. I personally find X2 an average Joe.

For those who don't want to invest in a separate amp, the X2 is a decent endpoint.

Crystal clear sound and very good bass is importent to me (electronic music head, not basshead tho), will HD650 give me this when amped to the next level?
HD650 + Rag is good?

Very low bass is not the 650's forte unfortunately. What there is though is articulate & well defined. The like of Röyksopp sounds superb.

To a certain extent that depends on the actual recording. Tracks such as the one below sound absolutely superb via my Project Ember & HD 650's..

https://www.youtube.com/watch?v=Ma27diEPqB0

It might be better to wait for the opinions of others since my experience of high-end headphones is rather limited. I can only say that the only weakness I've experienced with the 650's is in their reproduction of large scale classical music because the soundstage just isn't big enough. For everything else though - and especially considering the price - these are my end-game headphones.