you don't "need" an HDMI receiver to enjoy Blu Ray.
for the Dish DVR, it only uses "legacy" dolby digital anyway, so you aren't losing anything by going HDMI video straight to display and digital audio straight to receiver
for the Blu Ray, you can run HDMI straight to display, and have two options for audio to the receiver:
option 1 - just use a digital audio cable (optical or coax). this option has the ease of simplicity, but you are limited to a "downmix" of the hi-res audio on Blu Rays. it should still sound great this way though.
option 2 - as mentioned by oztech, if you purchase a Blu Ray player which can decode the hi-res audio internally, and has multichanel analog outs, you would hook it up to the 4800's multichannel analog inputs (like an SACD player) and let the player do all the decoding/processing, and you would just be using the 4800 as the amplifier. This would give you access to the full, uncompromised hi-res audio quality, but you may need to spend a little extra to get a player that does a good job of decoding/processing and has analog outs, and you have to run SIX cables from the BDP to the AVR.