HTPC Advice - HD Video/Audio via HDMI to Receiver

Hello, I am not an expert on AV terminology, so forgive any obvious mistakes.

I am building a new HTPC and would like advice on a few key elements. I will be using this for a large collection of DVDs and Bluray Discs all on NAS (ISO for BD and folder structure on DVDs). Cost is not an important factor here, I don't want to waste money, but don't mind spending extra where needed.

I'd like input on the best way to configure the system to support sending both HD video and HD audio signals through one HDMI connection to my Pioneer Elite SC-57 to process and play all content. My Pioneer receiver is connected to typical 7.1 speaker configuration. Video passes from the SC57 to a Panasonic VIERA TC-P65VT30 65-inch HDTV.

I'd like the sound to be sent to the SC57 for decoding.

Absolutely no gaming needed, just movies, music, some Netflix.

Questions:

Am planning to use a Silverstone Grandia GD08 case if that matters. Also trying to go as quiet as practical.

1) Should I use a MOBO and separate video card, or are there MOBOs that do a GREAT job of handling both through a single HDMI connection?
2) What MOBOs are best for this need?
3) If I need a separate video card, what are the best - using NVidia now, but definitely not a zealot; happy to hear best NVidia and best AMD cards for HTPC (if needed).
4) Do I need a sound card for any reason?
5) I have an Intel Core i5 Processor i5-2500 3.3GHz 6MB LGA1155 CPU from an earlier build I can use, but if there is a better option please let me know what it is.

Thanks in advance for your help!