i would agree with bryanc.. you need to put some limits in there.

if my guess is right, your system can push about 200 fps total, which is very nice (all the same res wow screens? any overlapped)

i'll assume no overlap and all the same size, so 200fps for the machine is what you have to work with. in that case, try these on all wows:

/console maxfps 60
/console maxfpsbk 30

that should give you; 30+30+30+60 == 150 at any one time

leaving enough for your browser