First off, beware that on many motherboards, certain PCI slots share IRQs, so you could help matters by shuffling cards around. Refer to your motherboard manual. That said, you seem to be running ACPI which means that this shouldn't matter.
What you can do is disable anything you don't use. For instance, I have disabled both serial ports, the parallel port, and the mouse port on my games machine because I don't use any of them - I'm USB only here. That's four interrupts freed. I only have one EIDE device, so only need the primary EIDE channel, but have a HPT370 RAID controller instead. See this:
IRQ 0 System timer
IRQ 1 ASUS OSD PS/2 Keyboard Filter Driver
IRQ 6 Standard floppy disk controller
IRQ 7 Microsoft ACPI-Compliant System
IRQ 8 System CMOS/real time clock
IRQ 12 VIA Rev 5 or later USB Universal Host Controller
IRQ 12 VIA Rev 5 or later USB Universal Host Controller
IRQ 13 Numeric data processor
IRQ 14 Primary IDE Channel
IRQ 16 NVIDIA GeForce4 Ti 4200
IRQ 17 3Com EtherLink XL 10/100 PCI TX NIC (3C905B-TX)
IRQ 17 Creative SB Live! Value (WDM)
IRQ 18 Lucent QuadraBus USB Open Host Controller
IRQ 18 Lucent QuadraBus USB Open Host Controller
IRQ 18 Lucent QuadraBus USB Open Host Controller
IRQ 18 Lucent QuadraBus USB Open Host Controller
IRQ 18 HPT370 UDMA/ATA100 RAID Controller