Hello -- I've strayed from HT for a while and now I am back I am looking to complete my system this coming year (new tv, speakers and a Sub)

So I currently have to work with:
B&W 602 S1 as mains
B&W LCR6 S2 centre
and a Denon 2801 Receiver

I'm looking to either pick up rear channels or move the 602s back if you think the newer series speakers deserve to be up front. (Rec'ns? - Stay with B&W or try something else?) I am looking for a small sub to round things out - I believe I don't have to go with the same brand, is that correct? (Rec'ns?)\

Thanks!