You can hook the Blu-Ray to the TV with an HDMI and then use a digital coax or optical cable into your receiver to process the sound. This is what I do because my Adcom receiver only has an HDMI by pass and does not process sound or video through HDMI.

That 805 receiver is very good and will do the job very well.

The reason to go with separates is because of 2 main reasons-

1- You get better quality parts and sound. For example, lets say you pay $1K for a receiver and compare it to a $1K power amp.
With the receiver, it contains a power amp, preamp and processor all in one for $1K. With the separate power amp, that $1K is all going to pay for just a power amp, so better parts can be used. The caveat is that if you go with a separate power amp, you will also need a separate preamp/processor to connect to the power amp. So you will have to spend another $1k or so for a total of $2k compared to just $1k for a receiver.

2- Separates give you flexibility. If you ever decide that you need more power you can buy a new amp and keep your preamp or if the features on your preamp are old, you can keep the amp and buy a new preamp. Also, you can fine tune your sound by mixing and matching different amps and preamps. For example, lets say you have a solid state amp and preamp and decided you wanted a warmer tube like sound. You can buy a vacuum tube preamp to use with your solid state power amp.

I hope this helps some.