Sennheiser PC165 and creative xfi extreme music

hi guys, i was looking at gettin a set of Sennheiser PC165 or the PC160 headphones for my machine but ive noticed that the pc160 has 2 audio jacks one is for input and the other for output so ive heard im curious as to weather it will work with my current set up i have the creative xfi extreme music sound card running a set of 5.1 speakers their the logitech x530's and on the speaker it has a headphone jack and on the sound card i have the microphone jack so if i get the Sennheiser PC160 headphones will i need to have 1 audio jack pluged into the speaker and 1 at the back of the pc cause that would be a pain..... or the only other way to do it is to unplug my 5.1 speakers everytime i want to use the headphones which will mean a turn off and start up when i want to use them.

the other question i have is if i get the Sennheiser PC165 version which is USB this set actually has a sound card built in and it would fix the problem that i described above but im wondering if the sound card that is built in to the headset is as good as my xfi extreme music and will it conflict with my xfi sound card