I can't see the video you're referring to other than a preview, I guess for some reason I assumed you were referring to a free youtube vid somewhere.
What you're referring to as stepping is usually referred to as aliasing, and as you pointed out is characteristic of any digital signal that's emulating analog tone, just like the example you cited with CDs. Throughout history, in most scientific blind studies, most folks fail the test of being able to consistently choose which signal is analog and which is digital. Many of the better softsynths have a way for you to control the quality of the aliasing (higher quality uses more CPU), but most find the difference so indistingushable that it's more of a "peace of mind" or maybe I should say placebo thing. The other big characteristic of true analog is "drift", where there is a slight amount of inconsistency in the harmonics (i.e. subtle pitch changes), and a lot of good soft synths will even emulate that.
Anyway long story short, I don't think what you experienced in the video will be an issue you encounter with soft synths or the Virus. There are folks out there who have sold their CS-80 boards or Jupiter 8s in favor of the Aturia software emulations because they truly could not tell the difference once the audio was routed similarly.
Best thing about soft synths is you can always try the demo before buying, and the price is right.
If you download the Zebra2 demo, be sure to grab some of the free patches off the site to test drive. In my opinion the factory patch banks do not even hint at what this beast is capable of.
If you'd like something a little easier to jump into, grab Dune
http://www.synapse-audio.com/dune.php
Another one to check out that sounds warm is Sylenth1