I have been using two FireWire soundcards, one for the host computer, and one for the Pacarana. Those are interconnected using a pair of ADAT optical cables. That way software on the computer can not only receive Kyma audio but also send audio to Kyma for processing. Its a really smooth way of working and a great way of bringing Kyma into your DAW workflow.
A few things to watch out for. First, one of the two soundcards must be the "clock master" so that both soundcards have their sampling in sync. I have found that having the computer soundcard serve as the master clock works best. The ADAT connection from the computer soundcard to the Pacarana's provides the reference clock. One thing that is tricky about this is that you still need to manually set the Pacarana's soundcard samplerate to match what you have set the computer's soundcard.
If your specific soundcards only support ADAT from the Pacarana's soundcard to the computers then you may have to have the Pacarana's soundcard become the clock master. Check though whether you also have S/PDIF connections available from the host soundcard to the Pacarana's. That can also be used for providing sample clock synchronization, and it also affords two channels of audio sending from the host to Kyma.
If you do not want to hassle over clock synchronization then one solution is to use standard analog connections between the two soundcards. That also has the advantage of being able to operate yor DAW at a different sample rate than the Pacarana. So, for example, you could elect to have a Kyma sound processing audio at 96 kHz while you are still recording at 44.1 kHz.
The second potential issue is FireWire bus bandwidth. For most computer set ups there is but a single FireWire bus (even if there are multiple FireWire connections on the computer). When you have two soundcards set up in the above fashion then there are three total uses for the FireWire bus: the computer's soundcard, the Pacarana's soundcard, and the FireWire connection between the computer and Pacarana that Kyma uses for all communications. You can run into FireWire data bandwidth limitations in such a set up if the soundcards offer many I/O channels, or if you are using a high sampling rate like 96 kHz. This is further aggravated if you actively use a FireWire external hard drive while operating Kyma and your DAW. Also be careful about mixing FW800 & FW400 devices on the same bus as the slower device will cause the bus to drop down to the slower rate whenever it is actively transfering data.
One way to address the data bandwidth limitation is to set up a separate FireWire bus for the computer's soundcard and any FireWire external hard drives; the Pacarana connection and Pcarana soundcard are then on its own FireWire bus. Desktop computers that can add internal PCIe cards, like most PC desktops and the older Mac Pros, can do this with a FireWire card. Unfortunately most all-in-one computers like iMacs, and notebook computers, do not allow this.