My old mITX board has Realtek ACL662 chipset and it sounds pretty crappy with basic headphones. I'm building a new PC and would like to know if ALC889 (this is the best onboard audio chip available right?) is much better than my old one or if I should buy Xonar DGX to go with the new motherboard? I will use the onboard audio with headphones (will buy something under 150€) and "small" active 2.0 speakers (some speakers that have amp built in so I don't need anything between the speakers and PC). I play FPS games mostly and CSGO the most which will need to use stereo or headphone setting to get the most accurate sound). For other games and other stuff I will have HDMI going from the PC to my AVR which is connected to TV and surround speaker set. So the PC onboard audio is only used when I sit in front of the PC.
The sound card decides if I have to go with mITX or mATX motherboard and case. So I will have to choose if I get the sound card or not before I can choose what motherboard or case I'm going to buy.