Hi, DM has asked me to look in and see if I can help at all.
I'm running Cubase5 on my AMD System along with an M-Audio Delta1010 Audio Device. I also have an M-Audio 2X2 Anniversary USB Midi Interface linked to a Roland XV5050 and Yamaha CS6R and an Axiom49 USB Keyboard.
The issue of shared IRQ's is not something that has caused me a problem and My Delta1010 is using a shared IRQ quite happily. However, initially setting the Audio buffer size incorrectly did cause a problem with drop-outs and crackling.
Have you disabled the on-board audio chip? Experience has taught me that this is a good option as it removes the chance of audio conflicts.
The advice to disable the Energy Saving features, in BIOS, is also good and is something I do as a matter of course.
Do not even think about Overclocking your system, unless you want to have a lot more grief.
If you are not actually using the Floppy Drive this is another thing you could safely disable.
It would be better if DM or someone else advised you on the features you can safely disable in BIOS, as I'm not familiar with the Intel Platform but the more things that you can disable the better, especially if you are using this PC as a DAW.