7.1 audio in 5.1 setup?

[reyz]

With a 7.1 receiver like the Yammy V663, is it possible to create a 7.1 audio experience with a 5.1 speaker setup (aka the creation of 2 invisible channels behind you)??

Have read somewhere before that this is possible but want to seek some solid clarification... as it will determine whether or not i dip for 2 more rear surr. speakers.

Also, is it advisable to bi-amp your front speakers if your receiver can already comfortably power them on a single amp per channel?

my yammy rx-v663 min rms output is 95w/ch and max power is 135w/ch
but dynamic power on 6 ohms can do 165W according to the specs.

for ease of reference, my front speakers type are a 3-way bass reflex design
and specs:

200W dynamic power (max)
Input Power (Maximum/Normal) : 200 W / 50 W
Sensitivity (dB/2.83V,1m) : 88
Freq response : 40Hz-50kHz
Tweeter : 2.8cm aluminium dome
Woofers : Dual 12.5cm Advanced PMD Cone
Impedance : 6 ohms

Am currently starting up a HT in the living room and have the display and receiver down-pat. The 5.1 speaker setup i'm looking to get and am one step away from doing so is in my sig as well