I've used SoundSoap, SoundSoap Pro and the de-noiser in Soundtrack Pro. RX puts them to shame. I would go so far as to say there's no comparison. Definitely grab the demo, but make sure to know what you're doing. There was an introductory discount period, during which I tried out the demo...incorrectly. I passed it off as just another product that didn't live up to the audio demonstrations on the website. I then had a job that required de-noising and the aforementioned tools weren't cutting it. I tried the RX demo again, but read the manual beforehand. After a "doh," and a few clicks, I had a wonderfully cleaned-up piece of audio. Unfortunately, the intro discount period was well over, so I paid full price. Looking back, I don't mind so much, since it has paid for itself many times over.
That all sounds like a fake testimonial, but it's genuine.
I also wholeheartedly recommend the Blade Runner set in HD, but that's for another forum. 😉