It's not really all that weird. You can't use an on board sound card with Sonar and ASIO drivers.
It is always recommended that you disable the on board card to prevent a conflict.
Under ASIO you can only have one audio device. Use the Mia only.
No one uses the on board MIDI sounds anymore, you use soft synths period.
If you need MIDI input from a keyboard/controller then you need either a audio interface that has MIDI inputs or use a USB controller.