You have to connect various components' video connections directly to your HDTV. The audio/surround sound connections can still run out to your receiver though, of course this will depend on the options of the various components you have in your system.
With DVD players/older receivers, I normally use Component video (RGB) to the HDTV, and digital optical to the receiver. In fact, bypassing the receiver can help provide slightly better PQ in such cases sometimes.
One correction though. You actually have a blu ray player and not a DVD player. That would preferably connect to the HDTV using HDMI, while using a separate digital coaxial cable to your Marantz receiver. There may be one setting on the blu ray player to select the audio output correctly (digital coaxial instead of HDMI). Look in the manual.
I have a Marantz SR9200 which is a great receiver and a Marantz BD7004 DVD player, connected to a set of Paradigm speakers - 5 plus a Sub. Unfortunately no HDMI output on the receiver (back then did not exist)
What are my options to connect to a HDTV without losing any image quality (barring of course spending another $2500 on an equivalent, but up to date receiver)