Play Fi query

[KNasir]

Hi Guys

I am new to this forum. I have a Paradigm PW Sound bar (3.1) with REL Sub . There is an option to add 2 rear speakers via Play-FI so can some one kindly guide me what are the most economical options I can look in to ? Also if some wants to sell their rear surround play - FI enables speakers kindly let me know.

Thanks in advance and have a great day !