As long as the speakers' impedance isn't too low on the Samsungs not a big concern, and maybe not even then (if they came from an HTIB sometimes that's a concern). For surrounds, mixing different speakers doesn't mean a lot for movie content. Usually you want matched L/R/C up front as the major concern. Brand doesn't matter much but rather their specifications. Mixing different subs can be more difficult, tho. If done well and you have a sufficiently sized room you might like 7.2 more, hard to know. What are the dimensions of your room and where is your listening position?