I'm not very familiar with APIC nor IRQ stuff, but according to the readmes of the PCI card manufacturers in my box, it's not such a good idea to share interrupts on any of the following:
- wctdm (Zaptel)
- bt878 (DVB-S)
- saa7133 (DVB-T)

According to the IRQ table, the PCI-E graphics card and the Zaptel card are both on IRQ16:

Code:
           CPU0       CPU1       
  0:       6217     273641   IO-APIC-edge      timer
  1:          0         10   IO-APIC-edge      i8042
  6:          0          3   IO-APIC-edge      floppy
  7:          0          0   IO-APIC-edge      parport0
  8:          0          1   IO-APIC-edge      rtc
  9:          0          0   IO-APIC-fasteoi   acpi
 12:          0          4   IO-APIC-edge      i8042
 14:          0         49   IO-APIC-edge      ide0
 16:      12812    1146464   IO-APIC-fasteoi   wctdm, nvidia
 17:      17306     750841   IO-APIC-fasteoi   bttv0, bt878
 18:       2431      84523   IO-APIC-fasteoi   saa7133[0], saa7133[0]
 19:          0          3   IO-APIC-fasteoi   ohci1394
 20:          0          0   IO-APIC-fasteoi   sata_nv
 21:         16        942   IO-APIC-fasteoi   sata_nv, HDA Intel
 22:       5556     254420   IO-APIC-fasteoi   sata_nv, ohci_hcd:usb2
 23:       3149     112234   IO-APIC-fasteoi   ehci_hcd:usb1, eth0
NMI:         99        116 
LOC:     279801     279782 
ERR:          0
Is it possible to use IRQs below 16 (such as 10 or 11) for PCI cards as well, in other words get either wctdm or nvidia to move to a lower IRQ?

Many thanks for your help, -sven