How about just getting a Digimax and adding 8 channels via the ADAT. I'm running a FW-1884 and converting my pres to ADAT via a Tango. So I can track 18 tracks at once. You can do the same with the FW-1804
I don't need to have more than 8 inputs for the moment, and for sure i'll buy a rack of 8 preamp cause there are only 4 on the 1804 and I want to replace them and add 4 more on the trs input. Now I checked the Presonus Central station and it seems very nicefor the monitoring. I heard that you plug it in the L/R main outs (monitors outs) of the FW-1804. Is that right ?
The Digimax is 8 pres with Adat out put that will intergrate perfectly with your Tascam. If you want something chaeper you can a Behringer ADA8000 which has 8 channels of ADAT.