Don't do that.
Get a separate SCSI controller, this purchase will outlast your next two or three mainboards. LSI cards aren't as outrageously overpriced as Adaptec's (even the onboard solutions) are, Tekram's even less so (these use LSI chips, BIOS and firmware).
Then, with three or four bandwidth hungry PCI clients present (2x Gbit ethernet, 2x SCSI usually), you WANT to use a chipset that has 64-bit 66 MHz PCI busses, or better yet, PCI-X. So if it's going to be P4, opt for Intel's 7505 chipset or ServerWorks GrandChampion.