I just got the Epson R1800 - 13x44 max with roll paper.
It's working great under 10.4.8 via FW and I just got it hooked up to the XP piece of "wonder" via USB and it's printing - sounds totally different though??
Anyway, it's not big enough for you - but i've heard good things about the new Epson - the 3800? 4800? But apparently it has big ink containers, which might make it hard to use it all in 6 months.
The forums at dpreview have a lot of people using the bigger printers, that might help you some too!