I use Tjernlund M-6 fans and I'm very happy with them. They draw only one amp and the balance of the fan and the quality of thier bearings are obvious to me.
The 1.1 amp draw makes it worthwhile to me and it moves 530 CFM.
Tjernlund Retail Store—High Performance Metal Inline Duct Fans (Models M-4, M-6, M-8)