My home theater system is currently made up of a Harman Kardon AVR235 and the 5 piece Athena Point-5 speaker package (one center, and 4 bookshelves). I'm looking to upgrade the main L/R speakers and I was wondering what I need to know to make sure the speakers "match" the rest of the speakers/reciever. Should I stick with Athenas or can I go with whatever sounds the best to me in the store? I'm also wondering the same thing with regards to the sub? (Note: I'm looking to spend under $600 for the mains and sub).

Thanks in advance for any help.