Umm...
I think you are running aground on home theater because you come from a professional audio background. General rule of thumb is, these items don't typically mix in the way you want them too. For someone just starting to get into home theater I think it's best to keep professional audio and home audio separate from one another because it will A. simplify things, and B. reduce your costs (as insane as that might sound). By trying to make your professional mixer and amplifiers work with home audio equipment you're effectively limiting your options and increasing costs with specialty items in attempt to make something perform a function that it was intended for.
A PC cannot act as a home theater receiver. In order for a receiver to be a receiver it needs 4 essential parts.
1 - A tuner; typically FM and AM, but may also include Internet Radio, Sirius, or XM radio.
2 - A processor; to decode bitstream surround formats such as Dolby and DTS offerings as well as post processes that include bass management and video processing.
3 - A preamplifier; to control input selection and output level.
4 - An amplifier; powers the speakers in the home theater.
Now the audio card can perform two of these functions, the processing and preamplifier (only partial preamplifier function since it doesn't have more than one input). However this is no good unless you have powered monitors all around or you plan to use 5.1 surround PC speakers.
If you decide to go this route you lose the option to connect additional sources such as video game consules, DVD player, television (satellite or cable), or a Blu-ray player, just to name a few. Basically you're tied into using your computer as your only source for home theater and your speaker selection options will be limited and will be costly for a good arrangement. A budget arrangement would offer sub-par performance.
Let's assume you are able to nab a receiver for around $50-100 that is 5.1 and has on-board Dolby Digital and DTS decoding. Once you have this you're options for speakers are nearly limitless, as most budget oriented speakers will not be tasking for a budget receiver to work with.
So let's keep to the receiver idea and work from there. HDMI switching on a receiver may not be necessary either, so keep that in mind. If your television or display has enough HDMI inputs to support your devices then you don't "need" to have HDMI support on the receiver. If your concern is that you won't get the best sound from a source such as Blu-ray without HDMI I am willing to bet you and many others would not notice a large or any difference between a system connected with traditional SPDIF (optical or coaxial digital) vs. HDMI. I'm not in any way saying there isn't a difference, but the difference isn't huge and it would be difficult to discern without an outstanding sound system.
