ISP Decimator
I personally disagree that the MXR Smart Gate is the best noise gate pedal out there.
I have used the MXR Smart Gate and Boss NS-2, but I got rid of both after finally getting my hands on the ISP Decimator. It's very easy to use, and totally kills any unwanted hiss without affecting tone the way the NS-2 did and, to a lesser extent, the Smart Gate.
I would really, REALLY encourage you to at least try the ISP Decimator before plunking down the cash on the MXR - which is, in all fairness, a very good noise gate, but IMO not as good as the ISP.
Just my 0.02