If you are setting up a 5.1 system (maybe you said and I missed it), then you definitely want the speakers behind you. This gives you the sense of things passng over your head (like airplane flyovers and magic spells)
If you are setting up a 7.1, then the surround back should be behind you, and the surrounds should be to the sides.
The rear speakers are not super-critical unless you are doing SACD or DVD-audio. If you are running mostly movies, even a reasonably cheap set of outdoor speakers will provide decent sound.
The rears only get mid- and higher frequencies, which are the sounds best detected for movement. The human ear does not locate lower tones well (you'll hear the term "omnidirectional" alot), so most receivers do not send the lower tone to the rear speakers. Since you don't need a big woofer to support those lower tones, most any speaker will do for the back.
You may have heard about "timbre matching". This is very important for the front three speakers, but the spacing between front and rear make this alot less important.
If you do SACD or DVD-audio, the best set-up is supposed to be all the same speaker all the way around.
The long answer to your short question is those speakers and placements should work very well with the system you have.
