Currently,there is no PCI-e card available from any manufacturer.Digidesign have announced they are to offer one in January,and RME are working on it. MOTU (my own company of choice) have been really very annoying and unprofessional, and refused to announce even their intention to release this technology,which is a bleedin' nuisance,since I have a Quad sitting in its box in my studio,as I write this.PCI-e is, no question, the way to go for PCI technology in the near future,but,for some reason,the music industry has been very,very slow on the uptake.It's not as if it's been sprung on them,because PC hardware has featured this architecture for long enough.
It seems that music hardware future is being perceived as either Firewire,or USB,though optical is possible on the Quad,but supports only 2 channels.
Personally,I'm left with the options either to wait,and use the Quad as an ancilliary machine,over ethernet (which i did not want,because I needed the brute power of this computer to run as the main machine),or entirely replace my audio interface setup,which I also did not want.
I have RME cards in my PC and one other G5,and they are quite excellent,so I'd be very tempted away from MOTU,should they beat them in the race.
It's a dilemma,and I ain't happy.