advice for quad monitor setup

Hey,
Im building a trade rig and need some advice. Running 2 PCs each with dual monitors is becoming tiresome. I want to drive four 1280x1024 monitors with a single dedicated PC. Ive done some googling and it looks like the single 4 monitor cards are ridiculously expensive ($400 up in uk). I dont intend to do anything hardcore 3d like play fear or quake 4 (already have a gaming rig for that). I was thinking of throwing together a couple of cheap 6200's or 6800's into an sli board with 2gig of ram and either a A64 3700 or 4000 or x2 3800 dualcore.

1)Will two 6200s/6800s be able to cope with 40+ 2d graphs/feeds and browsers spread over 4 monitors with such a high combined resolution?

2)In quad monitor setup sli mode will be DISabled. Does this mean the work load is not shared at all between the gpus and that the second card is effectively just 2 extra DVI/VGA ports for the first?

3)If Q2) is the case and only one of the cards is 'dominant' then would it possible to use say a nice 7600/7800/7900 as the primary card and then just a cheapskate 6200 for the secondary?

I dont trade too hardcore so dont want to drop $400+ on a single card solution from nV or matrox if i can do what i want to do with standard gfx cards which can be easily recycled into secondary rigs at some point in the future. I would rather use nV cards (driver stability) as the rig could end up being dual boot (linux) or recycled into a rip/burn drone or linux machine - and we all know how good ATIs support is for linux.

Would appreciate any advice/suggestions. Thx.