Hardware Abstraction Layers: Some Clarification

Hi,

This is my first post here, so I'd like to first just say hello to all.

Now with the question. I've been doing a bit of reading on Hardware Abstraction Layers (HAL), but am left with a few unanswered issues which have arisen. From what I read, most all sources state that ACPI should be used for WinXP systems and the "Standard PC" (Which uses PCI Steering?) option for Win2000. Now, my question is why? It seems logical to me that since PCI Steering allows hardware a reserved IRQ, and not a single shared IRQ, it would be a superior choice for performance. What's more, what is different between XP and 2000 which causes this difference?

I am planning on upgrading my sound card this summer to an ASIO compliant device to allow for pure bitstream pass through. Will this be a problem since I use XP and thus ACPI? I've heard crackles can occur due to the stops on a single IRQ.

Anyway, there are a bunch of questions in there, but they all revolve around the same issue. I hope you can understand where my confusion lies. If not, let me know and I will try to clarify further.

Thanks for your help. I look forward to your answers.