Mate, you obviously never ran a 3 screen system. The extra few hundred bucks for the other 2 LCD screens will be the best money you ever spend on your PC setup.
I am just going through steps to have my entire hardware platform replaced. Currently I am running a D960 processor and two 7900GT's and the machine is hired out for a year so I need a new one. Check out my 3 screen simulator videos www.youtube.com/dinther
The next PC will be a Q6700 quad core processor and a single 8800GTX card with the option to add a second 8800GTX in SLI mode. Indeed I am looking at using a Triplehead2GO Digital box this time around. The sad thing is that that box won't do 3 x 1440 x 900 so in desktop mode things will look pretty crappy.
I don't see why NVidia would not allow a 4 monitor span using two cards. Now I spend the money for that second card on Matrox equipment instead.