Z0001, never confuse a player with a workstation. In this case, your HTPC is a player, and a player just decodes content. But a DAW is a creator of content - multi-track audio acquisition, processing, rendering, production - this is what they make workstations for.
Any Core i3 based PC can work as a player. With reasonable supporting hw it can play standard HD video. With an external good video card it can play BD video (BD video runs at up to 40Mbps bitrate.) And with a top-end video card it can even play great games.
But a DAW is a creator of content and that's a different ball game. Workstations required powerful CPU with matching powerful hw overall, not just a fancy video card. The cost adds up quickly, especially content creation apps. A workstation also require smart system tuning to match apps with OS and hw. A well-tuned workstation can improve up to 50%.
Before you start, learn all you can about how to build a workstation.