Ok...interesting question. Let's look at this from another angle, 'what is high end?' for a start, and 'do you need a high end interface secondly?'
In the bad old days of early digital and even pre-early digital...think 1977 when the first digital recording was made, converters were basic, unless you stumped up for some boutique converters, or indeed you joined the dark side of the force and brought into the Pro Fools rubbish. In reality what we're talking about is the dynamic range of the converters, and jitter or the clock signal that syncs the audio throughout the analogue to digital and vice versa signal path. The dynamic range of very early converters was about 96db or 16 bit as we know it. In comparison vinyl was only 64db. Now no early converters could take advantage of the full 96db range, and indeed even the best converters today cannot take advantage of the full dynamic range of 24 bit converters. For example most the prosumer Presonus and Motu stuff now offer about 118db of dynamic range, up from about 112-115 which was the standard about 7 years. I'm not sure what the high end convertors are offering in terms of dynamic range...if anyone knows??
Now the pertinent question is...do you need anymore dynamic range from your converters? and the answer is if you are an average Sonar user probably not, and this is why Sonar is such a great program...Cakewalk have implemented a software solution. This is the 64bitfp mix engine and their upsampling paradigm. By using these concepts within Sonar, you're creating almost unlimited internal dynamic range, and you're eliminating the problem of time based effects disappearing into the noise floor or sounding grainy at the end of the tails. This is why in the past you needed high end converters, because they helped mask and eliminate this problem.
There are a couple of caveats, firstly back to jitter. Jitter is the tiny errors that form between poorly synced ADDA hardware and converters, and can be heard in time based effects and when the noise floor is higher than the output of the audio signal - say if you were mixing an individual instrument. Now if you have a large recording session, and everything was being laid down in a recording studio all at once...say a classical orchestra or indeed a rock band...then the likely hood of jitter coming to bite you in the bum is great, but again if you're an average Sonar user...this is not a problem with prosumer converters. You could easily record a band, probably not a close mic orchestra, and with Sonar's 'software' fix you won't have a problem. The issue is, if you start wanting to add in hardware based effects to the mix as you mix, and this is really the second caveat...by not understanding the digital medium, and the difference between celluloid and zeros and ones...the contemporary audio engineer/producer work within a hybrid paradigm, where they neither commit fully to the analogue medium or the digital medium. Furthermore, this is creating confusion as to converters and high end vs prosumer or the point of your question really. You see, if you're going to record with an analogue mind set...this is high quality outboard analogue equipment into a DAW, you need all the dynamic range your high end converters can muster, because all the stuff we enjoy within music...the tape compression and harmonic distortion gets lost or destroyed by both the lack of dynamic range...or it disappears into the noise floor once we convert our master file into 16bit...something I don't recommend by the way...16bit anything is obsolete, or the jitter actually makes the things we love to hear in our music sound distorted and grainy.
Hopefully this answers the OP, to conclude just in case they don't. Sonar doesn't need to create high end audio interfaces or indeed does any other company for Sonar...as I've said, unless you're doing true proper high definition audio or indeed you're transferring Beatle tapes and the like into the digital realm...high end anything is nothing more than a marketing ploy used to give teenage boys and now some girls gear envy. What this does is hold back emerging talent from really harnessing the potential of our technological eco system software instruments...Sonar. I will have to do some research to see how the other big DAWs have implemented a software solution to a hardware problem, but I think Sonar are still ahead of the curve in regards to this matter...I mean it wasn't until 2012 or around about then (off the top of my head) that Pro Fools introduced 64bitfp. Sonar introduced 64bitfp in version 6 wasn't it??, of course Pro Fools had their proprietary 48bit hardware fix.
Ben