My current computer has the Intel i7 6700K, 16GB 3200 RAM, and the MSI Z170A Gaming M3. Will I need a audio card?

For my old computer I used a basic Sound Blaster Live audio card and Cakewalk X3 worked well. I've been told my new set-up works at least as well as is compared to the previous 1 with the SB Live card.

Thanks.

Soundblasters have a pretty bad reputation around here...
 
'Need' is a strong word, but you'll have much better results with an audio card (or more likely an audio INTERFACE).  What you should get will depend on what you want to send into the computer.  For me, the Focusrite Scarlett 2i2 is nearly perfect.  I should have gotten the Scarlett 2i4 - the same model but with MIDI inputs.  This is great for sending one or two lines into the PC (separate guitar & vocals, for ex).  
There are lots of brands, price-points, and opinions.  the only universal opinion seems to be to NOT use the Realtek audio chip that's embedded in most computers.
 

Slugbaby
Soundblasters have a pretty bad reputation around here...
 
'Need' is a strong word, but you'll have much better results with an audio card (or more likely an audio INTERFACE).  What you should get will depend on what you want to send into the computer.  For me, the Focusrite Scarlett 2i2 is nearly perfect.  I should have gotten the Scarlett 2i4 - the same model but with MIDI inputs.  This is great for sending one or two lines into the PC (separate guitar & vocals, for ex).  
There are lots of brands, price-points, and opinions.  the only universal opinion seems to be to NOT use the Realtek audio chip that's embedded in most computers.
 

Thanks. I will not be connecting an MIDI or audio devices. I use only virtual instruments. Does that make a difference in your opinion?

I think you'll still need something to process the Digital-Analog conversion when sending the sound out to your monitors.
I can't recommend anything specifically suited to having no audio inputs, but getting something with a simple in and out option will work (such as the scarlett series).  

I think it very much depends on what you do. If you're recording live audio you should get a real audio interface. If you're writing with virtual instruments and rendering to WAW or MP3, I don't think you need anything, and I don't see how having an interface would make any difference.
 

jimlau
 
Thanks. I will not be connecting an MIDI or audio devices. I use only virtual instruments. Does that make a difference in your opinion?

Absolutely that makes a difference. You are only going to be using your audio interface to play stereo wave files coming from the SONAR mains out. That is about the same as playing a CD from your CD player and makes no more demands than that, so your built in onboard audio should be more than adequate. You can connect your monitor speakers or external amplifier with a cheap adapter even from a standard headphone jack. Try it and see. If you need more in the future buy it when you need it. 

slartabartfast
 Try it and see. If you need more in the future buy it when you need it. 

After reading Allan's comment, i was going to make the same comment.
I alwasy assumed that the processing power for the synths vs the onboard sound would cause issues, but it's not a setup that I'm familiar with.
 
"Try it and see" is always good advice.

And there's the new Wasapi mode drive that seems to let many people happy with the low latency it gives.

Of course, if you have the latest version of Sonar (Artist, Professional or Platinum).

i would see how you get on.. the DAW's I use now, can just about get by with a laptop if I really need to, but not for recording anything live like vocals. I'd say get a card dedicated though, it's partly about latency.. and partly about the quality of output.
 
if you do want a soundcard, try to think where you will be in 2 years, expanding wise.. otherwise you buy a cheap option.. then find later you need to spend more money further down the line.