I'd second mike c's comments.
You definitely want your front three speakers to be a 'sonic match', so when sound pans across them it sounds consistent.
I have a couple of bits of surround music which pan around all five speakers, so it's nice if they're all a good match, but this is generally less critical.
A sub can be from any manufacturer, but make sure it 'fits' with your system. I tried a well reviewed Velodyne unit with my setup, and it just didn't work. In an ideal world, the roll off between your speakers and sub should be transparent.