@acp_xt - ebay is full of fakes, hence the reason for buying direct. But its pot luck if you get stung.
Update on the Noctua NF-A4x10.... Its a perfect fit, but only a fraction quieter. I think the reason for the noise is down to the poor casing design of the 7604, the air slots on the side of the case near the fan are what are making the noise. The Noctua is quiet without the case on. To reduce the noise, I'm taped down two of the outer air slots which has reduced the noise to an almost acceptable level.
If anyone can come up with another way to make this silent, let me know
P.S. Put in a dispute with the seller and got $20 back That'll nicely cover the cost of the replacement fan me thinks