3d rendering problem

my computer takes much time to render in 3ds max and maya
even my system config. is

intel i7 extreme processor and intel extreme board Dx58so2
16 Gb ram
2 GB asus HD 6970 Graphics card


still rendering is slow
but my brother has

intel i-3 processor
ram 4GB
1GB nvidia 9400GT

his rendering time is faster than my system

i think graphics card not support well to my processor
so i planned to change my graphics card to 2.5 GB nvidia-quadro-5000
but it is so costly

because of slow rendering my workflow becomes slow

is my decision correct ?
anybody please give me reply with details