So Universal Audio tests several DAW software for compatibility in Windows but SONAR isn't one of them. I wonder why? 
 
Also, anyone using the UA Apollo Twin MK II successfully with SPLAT? I  just got one, but may return it, as apparently you have to have a current enough MOBO that supports Thunderbolt, and if you want the latest incarnation of Thunderbolt, v. 3 an adaptor cable to boot, if I understand that right. Shoulda researched more, but the awesomeness of the plug-ins and quality of sound had me buy before maybe I should have, as my system is about 6 years old with no onboard Thunderbolt support as far as I know, and I'm unsure if an add-on card would even work (windows 10 pro 64 bit, ASUS P7P55D LE MOBO, Intel i5 quad core @ 2.66ghz, 16 gig DDR3 memory, SSD main drive, SATA 2nd drive). It's such a drag trying to keep re-purchasing things to keep this thing compatible with that thing, etc. Looking briefly into Thunderbolt ready MOBO's after the UA purchase , then I find they all take only DDR4 memory, another upgrade requiring more $$, and needless to say, my i5 may or may not even fit the newer , thunderbolt capable MOBO's CPU socket, so potentially would need new cpu, and who knows if the ever changing power supply specs for my power supply would match the connector  for the new MOBO! lol.... I have USB ports but not the type C that the UA Twin takes and probably only max at USB 2.0. Don't really feel the need to upgrade since it's never been a speed issue in SONAR. That leaves two choices, new pc/components or new interface...Thoughts?

New computer!😃😃😃

There are problems with the Apollo on PC - UA uses thunderbolt for everything but the twin, I believe.  So it ain't SONARs fault, but trying to use the Apollo on a PC.  either return the Apollo or get a mac and learn a new DAW or get someone to build you an appropriate PC - maybe.  

Lynx?

There's an Apollo twin usb 3. You need usb3. If you have usb 3.0 maybe they will swap it? This is much easier than replacing a mobo. I am considering the usb 3 option since I have that connection on my mobo. 
 
EDIT- I see you don't have usb 3.0. You might still have an add in card option. 

I have the Firewire version of the Apollo 8 and it works like a hose.  You can get a TI firewire 800 card for like $40 or so. 

http://www.uaudio.com/audio-interfaces/apollo.html
 
 

BTW- it irks the crap out of me that the major manufacturers rarely support Sonar.  I used to use qbase and switched due to no tech support and countless issues with various incarnations of that DAW.  Sonar is more stable and does not appear to be missing features. 
 

Why must the audio interface be an UAD?
You can work with the awesome UAD-Plugins for example via extern 2-Satellite Quad (over firwewire which works very well with SONAR). And then use any other audiointerface like RME.
I don't believe that an UAD audiointerface ist better than a standard industrie audiointerface from RME.
We work with a 2-Satellite Quad for over 2 years and its very very stable. Never had a problem (Windows 10 x64)

I have the Apollo Twin MkII, which UA users tell me must have a Thunderbolt compatible MOBO....I may send it back and try the RME Babyface since that should be OK with USB 2.0 and my current system...I hope.
 
The really killer part of the Apollo Twin of course, is those mind numbingly famous and supposedly awesome realtime FX on your inputs that don't ding your pc's CPU since all the processing is down there.
 
One day, maybe DAW's will be intelligent enough to where they configure themselves for any hardware interfaces to the point that no secondary  software for the interface itself will be necessary. It will all be handled in the DAW.