I had a similar experience at Harvey Normans.  One of the Home Theatre guys (who's quite prominant in the store, but not sure of his 'rank') tells me I need to buy the more expensive receiver because the cheaper ones wont allow the HD audio on blurays because the PS3 'can't handle it'? 

The PS3 has all the HD audio logos printed on the side of it (bar DTS Master which was added later as a firmware update).  A bit more investigation shows the PS3 can't pass (bitstream) the HD audio signals to the receiver to decode anyway, so there's nothing to be gained on that front no matter what receiver you pick.  (Though obviously there will be other improvements as you go up the models in other areas).

I think people who buy the more expensive gear are still going to be happy as undoubtedly the more expensive stuff will still sound good.  It's just they could often have the same end result for less.