If you get a receiver that is HDMI 1.3 compatible and will decode the newer HD audio signals you should be fine. The easiest way would probably be to run your cable box and HD player to the receiver and then HDMI out to TV.

It's the HD audio that gets confusing, you can receive the uncompressed HD signals either via multichannel analog outs, it is passed via HDMI in PCM or supposedly the 1.3 HDMI and newer units will do bitstream but I'm not sure if that will work with current movies. Dolby's website talks about an authorization that has to be encoded on the disc to allow the bitstream to pass and I haven't been able to find information on how these new receivers and players deal with this.

I don't understand what you were told about the Marantz. I know some low end receivers will pass HDMI video but not audio, some will convert analog to HDMI and pass it, some won't, you have to look at the features to see what it will do. I think if you get a receiver in the budget you mentioned that is 1.3 compliant you should be alright, or just ask here before buying. LJ will set you straight.