polki: It did mention models but I cannot remember exactly.
I did do significant research on the vsx-520 model and as such i am sure I would have noticed if it said 420 on the price tag.
I guess I can't really make a case until I have a copy of the receipt, if the receipt says 420, I will pay the difference if possible.
If it says 520 then I feel the unit is rightfully mine.
I am awaiting a call from my friend as I type.
Thanks thus far for your opinions.
But if the 420 is not going to be good enough, you would be better to just give it all back and cancel it. At the end of the day they screwed up, not you.