Dumb Question

I have an HK AVR 85 that had been used for 2 channel system.
I have been trying to create a HT system on budget and need some advice. I have two B&W Nautilus 805 for front, just got a ASW675 (have not hooked up yet), a small Infinity for center channel and some old speakers for rear.
Problem is, with my current set up, even without the Sub, I can barely hear the sound out of the rears.
I am totally at a loss on how to add to the power of the HK.
Can you guys recommend any amplifier that would complement the Harman Kardon AVR85?
I would like to go for a 7.1 reciever in the future...but not immediately.
Thank you.
Thank you both for taking time and answering my question.
I am grateful especially to Sailfishben for debunking the 7.1 myth and recommending an amp. There are so many out there, it could get downright scary for novices like me to choose the right one.
Thank you Chadnliz for your comment about the hype about the rears.
God bless!
I agree with sailfishben. 5.1 is enough & buy a good 5 channel amp. You can get a parasound/anthem or similar for $500 to $800. Also, consider a better center. You won't believe the difference a few hundred will make with a decent center (b&w-not nautilus series???).

What are your rears? Are they worth it? $100 for a pair of little used somethings may work way better?
No such thing as a dumb question. I will also agree with sailfishben, a few years back I bought Harmon Kardon's flagship receiver (AVR7200---7.1), it now sits unkooked in a spare TV room.
Take your time, do lots of auditioning and let your ears tell you what you really want.