Author,
I understand. It can be quite confusing. I built my HTPC last year, and upgrade most of my components. I decided that the receiver is the heart of my system, hence I bought the Marantz AV8801. This receiver has excellent DACs and will give you great sound. Also, I found a huge improvement after adding Kimber cable speaker wires.
The other challenge, because my speakers are Paradigm S6s and S2s (rear) plus subs I require good amplification otherwise I risk damaging my speakers. I went with an Anthem amp (7 x 125) With this out of the way I required a way to manage my digital library.
The problem is, every time I look into building my HTPC I found that it required a couple grand. Finally, I decided to build one. I used an ASUS Extreme6 MB, I7 processor, GeForce GT640, modular power supply, 8 Gig Corsair memory, 120 Gig SSD for the OS (recommend using 256) and with recent upgrade 20TB of HD for data. This required a PCI raid controller card (but I didn't setup the raid) because I maxed out the number of available drives on the MB. There are 10 drives available with one free in the top of my case. This also includes the blue ray drive. To cool the system I'm using a Master Cooler. On my last build I used a water cooler which I prefer.
Music doesn't take too much disk space. I have over 1,200 CDs ISO'd and losslessly ripped. Movies, on the other hand, take ~ 25gig ea for blue ray.
There is a lot of controversy over raid etc, but my analysis determined that spanning the disks is the most cost effective. Raid is not true redundancy. My original drives are WD reds, but my recent upgrade I went with the blacks.
Next, to get the best video from the system I recently purchased the Oppo 103D. This is truly amazing. Now I'm running the HDMI out of my computer into the Oppo. I don't believe the sound is any better than running the HTPC straight into the 8801, however, the picture is awesome. I'm viewing on a Panasonic GT30 (60 inch plasma). The only issue is that sometimes the PC and Oppo get out of sync and I have to reboot the PC to get it to recognize the sound card in the Oppo.
The system is a bit complicated, and I have too many remotes. I have to switch the input on the Oppo when playing the computer. This is a minor inconvenience compared with the quality gained in the video. Hopefully I've answered your question. I've spent many years putting this system together and now it never fails to impress.