RE: ACPI or Standard Mode
Standard mode was useful several years ago when the PIII processors and the BX chipset were popular. At that time ACPI and the APIC standards were pretty new and didn't always work as well as they were designed to work with older hardware. If you installed in ACPI mode on most of those systems, the PC would assign most of your PCI devices to IRQ 9... which wreaked havoc on audio systems. This was due to hardware limitations within the motherboard, and not on the operating system. On newer generations of motherboards ACPI allows you to go beyond the old limitation of using only IRQs 0-16 assigning IRQs up to 23 with a limited amount of sharing. (You still have control over what devices share IRQs by switching which slots you use on the board.)
If you are using a newer system... say... maybe one that is fast enough to meet the recommended specifications for running SONAR in the first place, ACPI is the way to go.
There may be some special cases, such as Larry mentioned with the Creamware card, but I would bet that even then it's not as much of a necessity as it was with the older chipsets. (UAD cards are similar, in that you generally would like them to share if possible, but mine have been working flawlessly... well, except for that CPU munching thing that Cakewalk and UAD are trying to solve for all of us.)