Since your primary application is for running an RME sound card, why don't you simply build a second PC based on a used sandybridge board + CPU for that purpose? It'll be dirt cheap and the Z68/H67 chipsets are the last ones to have native PCI.
I did consider an option to build a second PC, however space is a huge constraint. I have a space dedicated for audio alone and that too now feels crowded. Also, explaining second PC to wife is a battle that i know I'll lose.