Your sound card will power the X1 with ease.
Plenty of opinions out there on the X1 the majority of them positive. For me the bass and treble are perfect, bass hits low and hard, this with a great sound stage really adds to the immersion in games and movies but it is also articulate enough to make music a great listen.
I must say that replacing the cable and after 50+ hours run in the X1 has only got better.
Higher than normal resistance on the stock cable can cause looser and slightly muddy bass.
I bought the £5 KabelDirekt Pro Series 3m cable and I think it's an improvement over stock.
I also got the KabelDirekt cable for my X1's, can't say if it's an improvement as I never tried the stock cable.
I'd seen most people recommended changing it anyway so didn't think there was much point trying it out.
Just get 80ohm Beyerdynamic DT770 pros then - no need for an amp
yes but you need the D2X for your home theatre speakers don't you?
How does your speaker system connect? Is it via discrete 3.5mm cables or SPDIF/Optical?