The VS-20 is more a demo/songwriting tool for us,yet it's unique feature wise. We've been seeking info on a 2in/2-out w MIDI interface, specific for SONAR Artist or above to replace current mobile rig. So many opinions and choices but we can't seem to find the thread in the forum dedicated to USB interfaces that the Cakewalk/Sonar users may be familiar with,that work best...Thanks. We use Studio One 3 as a primary DAW with much larger input count interface but have been having a lot of fun with Home Studio lately,fun and interesting,upgraded from an old Guitar Tracks vs.4.1.  Thanks

Yeah, I too have a VS-20 gathering dust. 
 
If you're a Studio One user, you might want to stick with one of the AudioBox interfaces like the 44VSL (four inputs) I used to own the 1818VSL, and its sound quality was superb, but it had absolutely horrendous problems playing nice with my USB devices. Half the time I'd turn it on I'd a huge amount of buzzing that wouldn't resolve until I turned it off or switched USB inputs. 
 
Right now I'm using the second generation Focusrite Scarlett 18i8. Four XLR/TSR inputs up front, four line inputs and optical and SPDF ins/outs on back and MIDI in and out. I had the first generation unit, which worked fine but I got a good deal on the second generation. It also comes with some nice Focusrite plug ins. There have been problems with the second gen series (you'll see a couple of topics here) in terms of the drives not playing nice with Windows 10. I was getting a bit of popping and dropouts playing legacy Sonar files loaded with audio. But I just upgraded to a faster computer with a dedicated SSD drive and 16gig RAM, and these files are playing perfectly, even with multiple instances of my UAD-Satellite plug ins running,  and the sound quality is superb.  I haven't yet recorded audio into it so that will be the next test. 
 

There have been plenty of interface threads, but not lately.
 
Try the TASCAM interfaces.  I've got 2 different ones and they both work fine w/ SONAR.  Most consumer/prosumer interfaces use the same ADDA chips and most of the preamps are similar too.  There is only so much design/material difference when you are dealing with $5 circuits.  It is the drivers that make the difference, and your computer configurations.  On the low end, just buy from a local or reputable online store so you can return your buy and switch it out for an item from Column B if A doesn't work out of the box.
 
If you want to go pro use Lynx.  If you have too much money or make a lot doing sound work get Burl.
 
Many here use RME - good hardware and great drivers.  But expensive.
 

I wrote out a shopping list of stuff to compair if your in the market for a new interface. It's down the page a bit but you can click the link at the top. 
 
http://www.cactusmusic.ca/Recording.htm
 
In the low end most folks here are using Focusrite, Tascam, Presonus and Stienberg without issues. 
In the hi end RME seems the leader as far as you never see a thread here with driver issues, but there's a few others like Motu that are worth looking into.