adding compression to track with hardware after recording

I assume you could send the audio out to your audio interface and record it's output to another track sort of thing.
 
Though Sonar has some pretty decent compressors (even some specifically for drums) available.
 
Yes, I could be wrong so you mileage may vary.
 
Good luck!

Personally I see no point in this. Traditionally we use hardware compressors while tracking to tame any overs. Once the track is recorded we can use plug in compressors on a track because you will maintain your signals integrity.
 
Running audio through A/D   D/A converters instead of staying "in the box" only makes some kind of sense if the converters and the compressors are very very high end. There seems to be a myth that you should run your audio through some analog gear to make it sound better.. This might only be true for the very high end gear. What we have as plug ins, if used properly, blows away most of the hardware that's affordable.   

Cactus Music
Personally I see no point in this. Traditionally we use hardware compressors while tracking to tame any overs. Once the track is recorded we can use plug in compressors on a track because you will maintain your signals integrity.
 
Running audio through A/D   D/A converters instead of staying "in the box" only makes some kind of sense if the converters and the compressors are very very high end. There seems to be a myth that you should run your audio through some analog gear to make it sound better.. This might only be true for the very high end gear. What we have as plug ins, if used properly, blows away most of the hardware that's affordable.   

I will say ^This^. But this is Sonar and the great thing about Sonar is that it can pretty much do whatever you want.

Cactus Music
Personally I see no point in this. Traditionally we use hardware compressors while tracking to tame any overs. Once the track is recorded we can use plug in compressors on a track because you will maintain your signals integrity.
 
Running audio through A/D   D/A converters instead of staying "in the box" only makes some kind of sense if the converters and the compressors are very very high end. There seems to be a myth that you should run your audio through some analog gear to make it sound better.. This might only be true for the very high end gear. What we have as plug ins, if used properly, blows away most of the hardware that's affordable.

 
Pieces of analog gear are often used for their characteristic quirkiness and are not necessarily expected to be neutral.

Lots of myths in the mix here...first off the "average" prosumer converter of todays products can handle frequency conversion FAR OUTSIDE the realm of human hearing...heck 10 year old emu converters will convert A>D>D>A with no perceptual loss in human hearing frequency ranges...this is a scientific fact of the Nyquist frequency formula...(see footnote if you doubt this)
 
The sound you send TO your compressor is exactly the sound you recorded (provided you did not tweak it in the daw, and even if you did it's still a perfect audio signal) so depending on what you want to do with it outside of the box is completely up to you...I send stuff to my SSL comp all the time and the difference is not subtle compared to my UAD or Cakewalk versions of the same compressor...there is absolutely NO degradation in exporting D>A and back in A>D but there is a TON of confirmation bias in this business so be careful what you believe...
 
If you want to be free watch the video in the footnote and check out the info...science is better than rumor.
 
https://xiph.org/video/vid2.shtml
 
https://www.youtube.com/watch?v=BYTlN6wjcvQ
 
(NwAVguy quoting AES paper:
Meyer and Moran played SACD content with the ability to switch an A/D –> D/A pair operating at 16 bits and 44 Khz into the signal path. In other words, the high resolution SACD audio was sometimes “down converted” to CD quality. They designed the test to give the listeners “every opportunity” to detect a difference. The testing lasted a year and included 60 members of the Boston Audio Society, many professional recording engineers, fresh eared college students, and a whopping 554 listening trials. After all that, the only way anyone could identify a consistent difference was by cranking the volume unrealistically high during quiet passages exposing the higher noise floor of the 16 bit conversion.
Think about the implications of the above. Most subjective audiophiles claim to hear differences between CD players, DACs, and indeed most anything that performs a digital to analog conversion. They also consider SACD and other high resolution formats as being plainly superior. Why can’t audiophiles detect any difference at all when the music is subjected to an extra A/D and then another extra D/A process when they don’t know that’s happening?) (here: http://nwavguy.blogspot.com/2011/05/subjective-vs-objective-debate.html)
 
p.s. I built the 02 headphone amp he designed (for less than $100)and it blows everything I have ever used out of the water 
 
 

Outs of the  interface to a D-Box/LT setup to a Langevin DVC to a Daking FET3 back into the interface to a new track which outputs to the D-Box digital in. 
There are plenty of YT vids on the D-Box and how to integrate it. 
 
I am also sure you could just get a Mackie mixer and use that as your summing device.

Congratulations.  You got some good kit there.  I found that the better the capture is, in the sense of sounding "finished," the easier mixing got.  A good front end can help with that.  Have fun!