45w per channel will be fine I should think, what fans and controller do you have?
Do you have a build log for your build so I can take a look?
Thanks for looking.
Fans and Controller
1 x Lamptron FC2 5.25" Bay Fan Controller - Black £24.98
3 x BeQuiet SilentWing USC 120mm Fan £14.99 (£44.97)
Total : £79.85 (includes shipping : £8.25).
No log yet, half is coming from my old rig inc. the fans, and the rest is on order.