Many thanks for the reply I had a look at the link you left and found that the 140mm triple will be too large so I plan to go with the 120 mm triple as the overall size: 410mm x 150mm. Actual filter size: 380mm x 120mm which will cover up the 140 mm spaces.
I can't run triple 140s as the case only supports x2 140s and x3 120s so going with the triple 120s
Furthermore I am running the x3 120 mm fans as exhaust, the reason for the dust filter is that I am afraid that dust will get in the NZXT source 530 as it does not come with top filters and therefore not dust proof what do you think?
for exhaust you do not need dust filters , simply put a cover or cloth over your case when not in use , 99% of dust will come from intake fans or mesh openings , concentrate on positive air pressure , more intake than exhaust this will help reduce dust in your case , personally i would never cover exhaust fans i don't see the need