You may not need anything but an H8000FW. I am not at all sure about how the drivers work, but the H8000FW should eliminate the need for a sound card (Nick please help!). Anyway based upon this premise I've been bugging a couple high placed people at Eventide to look at developing a couple options for using the H8000 as channel strips.
I'm using a H8000 (not FW and, yes, I have an Orville too) with an RME Digiface with an RME optical to AES/EBU converter. That was about state of the art 4 or 5 years ago when I bought the gear and was last active in recording. Basically I use Nuendo (2) because at that time ProTools had a seriously handicapped sound due to a cheap clock. Also Nuendo's user interface is much easier to work with than ProTools. The main advantage to RME's stuff was low latency and this all could still be the case.
I haven't received a reply here to my question on the subject, but I would think that H8000FW's firewire interface would have to be slower (higher latency) than a PCI card based system like RME's if you are using firewire hard drives, and possibly so under any circumstances.
I have both internal SCSI drives and firewire. I've found that I can get more tracks with the SCSI drives. Though SCSI drives seem to be extremely limited in capacity compared to firewire ones.
I am upgrading my Orville for a number of reasons. Though replacing RME's interface will probably just slow my setup down, I should be able to use the H800's optical interface to replace the AES/EBU converter, though I suspect with 4 instead of 8 channels. Nonetheless Eventide's marvelous matrix I/O system is a major improvement over RME's converter. Presently I am using the single stereo analog input in my H8000 as a Mult thanks to this and eliminating the need for cables that I don't have and are hard to get here.
I got most of my high quality cables from an online company in Nashville. Since my e-mail hard drive crashed I don't have the directions handy any more. I think I also got some quality cables locally.