Is there any way to buy 4 of these of aquacomputer
No.
should work fine on the aquero 6 xt without the need of any accessoires ?
Without the electric specification from the fan we cannot say if your setup will work.
What about where to buy the blanco PCB's ?
According to this review on the Akasa site;
http://tech-reviews.co.uk/reviews/akasa-120mm-apache-fan/3/
the fans use 0.33 amp each
16 of them on a channel is 5.28 amps ... just a little bit excessive for an Aquaero. Even 8 per channel would be pushing the capabilities I believe.
By way of contrast a similar speed corsair SP120 uses 0.08 amp
A build on a scale like this requires a fair bit of knowledge and skill. There aren't just commercial splitter PCB's to accommodate 16 fans because practically no one would buy them. In similar builds people usually create custom wiring harnesses themselves.
In this case if you want to do it you would need to wire each fan direct to the power supply and also run PWM and speed signal wires from each channel of the Aquaero to each bank of fans. That way the Aquaero is not powering the fans and there should be no effective limit.
What about the corsair SP120 High performance? they run at 0.18 amp x 16 = 2,88 amp, which is still to much for the A6 to handle right ? (and what about when i add a waterblock/heatsink on it ?)
if that is still to much, i might put 12 on that channel (12 x 0.18 = 2,16 amp, so that should be fine right?)
So that way it will be like this :
fan channel 1 : 12 fans,
fan channel 2 : 8 fans
fan channel 3 : 8 fans
fan channel 4 : 8 fans
Also what is the advantage of pwm vs 3-pin on the aquero 6 ?