If your in the market for 140mm fans the, Sharkoon System Fan 900rpm or the Akasa AK-195BL,
http://www.scan.co.uk/Product.aspx?WebProductId=756698 and
http://www.scan.co.uk/Product.aspx?WebProductId=876305
You might also consider the Yate Loon D14SL-12
http://www.chilledpc.co.uk/shop/prod...roducts_id=488
If you are considering reducing the number of fans remember that it is always better to pull more air out of the case than it is to push air in. I would probably fit 2x 140mm fans and the rear 120mm and then probably have a single 120mm on the front as an intake or 2 intake but at ~1000rpm.
Oh and for case fans the Scythe Slipstreams are very good, not so good on heatsinks but fine for moving air around in cases.