Just a note to say that when you implement ASIO support, please be sure to do it alongside the standard windows drivers as ASIO only supports one sound card at a time and not every sound card supports it.
By supporting both together we get the option of using a multi-channel card that required ASIO alongside other cards via WDM.
You should probably also provide a configurable output latency buffer for the ASIO driver so that we can sync the output from the ASIO card with that from a WDM card.