music is best 2.0
R1900T3 is best for music
C3 and R501MKII is worth the money

the r1900t3 is for serious music listening and not for blasting

2.1 is easier compared to 5.1

many people experience only the front speakers make sound and the center/sub/rear doesn't do anything
the reason why is because music is rendered as stereo and not surround
 

r1900t3 will make life simple
Edit:
oh...I've just noticed that the R501mkII is quite simple

good news for you,just plug the wires into the 'line in' port instead

you'll get stereo surround without having trouble thinking on how to connect them


never knew R501 was that simple compared to other 5.1 multimedia speakers

good to hear that you're choosing the r1900t3
it's possible to plug them with the x600 sub,just don't connect the r1900t3 into the x600 speaker out
connect them separately,you don't wanna burn your r1900t3 amplifier

is indeed C3 amp is weaker than the S330,that's why the rms is low
but normally we don't look at the power output to judge how loud a speaker can produce (you have to test them to know how loud it can go )

normally we think the heavier the speaker,the quality of the speaker built is better
we think heavy speaker means thicker wood used to build a speaker enclosure (so that it won't vibrate too much)

but it all depends on the design of the speaker if you're talking about sound quality,so leave that case alone
you can always continue your discussions here