Building up my new surround system

[limonv]

Hey guys.
i bought a pair of B5´s last year around september and i´ve been enjoying them so much. Ive saved some money and i think its time for another investment in speakers. I want to make my whole system of the same brand. i just have the B5´s so my question is should i go for the center speaker? should i go for the sub? should i go for the rear speakers?
i guess im thinking about the B6´s, to replace the B5 as fronts. but i dont know which is the smartest move, considering that i have the money just for one of the things. so what do you think is the best thing to do ??
im mainly using it for music and music dvds.

thanks guys, appreciate your help!!

[JoeE SP9]

What are B5's?

[limonv]

PSB image B5 bookshelf speakers!