So, a bit off topic but, this is the entire point of UAD Apollo unit. It is outside of SONAR... allows you to insert any of the UAD plugins for monitoring or recording (you have the choice). It also has a new mode called unison, which allows you to put a channel strip (including its pre amps) into the chain. So, if you want to record a guitar track, you could throw a 57 in front of the cab and then chose which preamp you want to use (a Neve, API or UA). They are still releasing new unison capable plugins including some of the guitar amp sims (the newer Marshall is an example).
The amazing thing for me is that these audio chains have near ZERO latency, no matter how many plugins you have in the Apollo. What I wind up doing is recording two tracks while tracking (one through the Apollo with effects and preamp and the other DI'ed). So, if I don't like the effected track, I can always treat the DI'ed one inside of SONAR or blend the original effected track with the DI'ed track.
It is such a pleasure to be able to record this way without having to worry about latency. It reminds me of the workflow of working with tape decks but with all the flexibility of digital audio. The UAD platform was definitely worth the price of admission to me and I would highly recommend this system to any one of my closest friends.
The cool thing about the APOLLO unit is that during mixdown, the DSP from the Apollo is available from within Sonar, so you get a 2 fer out of the deal (this great audio interface and additional DSP power). The only current drawback that I see is that UAD doesn't directly support Sonar any longer and their WIN 10 support is lagging (the latest UAD version 8.5 has documented problems with WIN 10, previous versions work fine). And the quality of the plugins is arguably second to none.
Jim