Some soundbars have multiple HDMI Ins/Outs. Some have Coaxial and Toslink Ins/Outs.
Some on the other hand only have one HDMI IN, and only analog in, with no digi connections other than the afore mentioned HDMI.
Depending on the model(have you decided on one yet?), you may not want the AVR going to the soundbar.
If the soundbar you choose has HDMI In and Out, then you could go: AVR -> Soundbar IN ->Soundbar Out to TV IN.
If the sound bar only has HDMI in, and no out, then you would want to use another form of connection for audio, hopefully the Sound bar would have Coaxial or Toslink. Otherwise, the TV would not get the video signal via HDMI.
Given your druthers, you would want a Soundbar with as many connections as possible: HDMI In/Out, Digital Audio In/Out, and Analog In/Out.
If you get a soundbar with only In, the you would need to figure out where to compromise.
OTOH, I believe BIC America has a "soundbar" that actually uses speaker connections for the surround. However, I cannot find a link directly.
By the By there is a soundbar forum http://www.avsforum.com/avs-vb/forumdisplay.php?f=195