ReaFIR is part of the ReaPlugs package

AFAIC the best program by far for serious restoration is iZotope RX, but even that can't violate the laws of physics.
 
Remember Anderton's First Law of Noise Reduction: "Noise reduction is most effective on audio that doesn't have a lot of noise in the first place." 

Cactus Music
 
You contradicted yourself by saying a Audacity can do this why can't Sonar?? Then you said that it didn't work very well. Sonar could add another useless plug in too.. but who would use it,, it won't work. 
 
The answer is this type of software does not come cheap
 https://www.izotope.com/en/products/repair-and-edit/rx.html
 
 This is why Sonar does not include it,, the price of Sonar would double.  
The tool for the job is found in many Wave editors, Audacity is free so you really can't expect it to include a $300 plug in.  
And the way it works is you add a Wave editor to your tool menu and this will be integrated into Sonar and your workflow will not be slowed down. 

I meant to say it didn't work probably because it was external and created inconsistencies which may not occur if such a feature was available within Sonar.
 
Anyways, having said that, I am inclined to agree that free or low-priced plugins may not near perform as well as say, an izotope plugin costing a few hundred $s. But right now, I am not prepared to put any money on new plugins. I am trying to make the best use of whats available and included in my arsenal.
 
Thanks for the suggestion of adding a wave editor to the Tools (or Utilities) menu. I just looked it up and guess it involves adding/modifying items in the windows registry. Will try that if I can muster the will. 
 
 

Adding any external program to the SONAR menu requires a registry entry but I tried to make the process easier with a program available on the Sonar Resources and Utilities thread called SONARToolEditor, direct link is here

scook
Adding any external program to the SONAR menu requires a registry entry but I tried to make the process easier with a program available on the Sonar Resources and Utilities thread called SONARToolEditor, direct link is here

Thanks a ton for all that info. Truly appreciate it.

I totally understand not wanting to spring for more plugins but I just wanted to add a vote for IzoTope RX. Definitely put it on your shortlist. And who knows what Black Friday may bring this year.

Sanderxpander
I totally understand not wanting to spring for more plugins but I just wanted to add a vote for IzoTope RX. Definitely put it on your shortlist. And who knows what Black Friday may bring this year.

 
+1 I believe the plug in pack for (De-click, Dialogue De-noise, De-hum, and De-clip) are only 129.99 USA bucks.
Though I don't use the pack on newer recordings, a lot of my work is "Conversation work".
I convert old 4 track, 8 track, 2 track cassette / 4 track, 8 track, 2 track reel / 8 track 1/2 inch reel tape to digital files.
 
I own a slew of old machines. problem is keeping up on their maintenance.
but a few years back I stocked up on belts and capstan motors and do my own repairs.
 
Back to RX, I use it to clean up old tape recordings and it does a great job.
I got to a point where studio hours were running low. once the digital age took over, everyone had a studio in their living room. So I turned to conversation work. You'd be surprised how many people out there want to revisit old recordings but don't have the means to hear them. but when they can import these old multitrack recordings into a DAW, they are ecstatic (not to be confused with static = which is what most of the old 4 track recordings sound like before RX 
 
Unrelated: A list of some of my machines -
Tascam 424MKII
Tascam 464
Fostex X15
Tascam 488MKII
Tascam 488
Tascam 388 Studio 8trk reel
Akai GX-4000
Sony TC730
Tascam 38B
 
 

There are posts here on Adobe Creative Suite 2.0 which can be gotten for free. Adobe Audition 3.0 is included (32-bit) which has the noise reduction tool the OP is requesting. I launch Audition (I have v4.0) as my default wav editor from the Utilities menu in SONAR for this function religiously.

The CS2/Audition 3 option is a free option, but need to dig into the forums for that link.

Both iZotope RX and Adobe Audition seem to be the best options without artifacts.

Anderton
.........Remember Anderton's First Law of Noise Reduction: "Noise reduction is most effective on audio that doesn't have a lot of noise in the first place." 

Cannot argue with that - SNAP!!

A Multiband expander can be pretty helpful. I'll make a video.