Here is a comparison of the Purifi based 2 channel stereo amps from VTV and NAD:
Cost: The C-298 NAD is $2K plus shipping and maybe tax. The VTV stereo amp is $979 with free shipping (30 day money back) with the stock Hypex single dual op amp per channel. If you want the Pro Sparko Labs discrete op amps with Sparko Labs regulators on each channel then it is $1350 with free shipping. Mono blocks using the Sparko labs combo are $1800.
Warranty: Same for both....2 years.
Sound: I would think the basic $979 VTV and the $2K NAD would sound close. NAD does not say what kind of buffers are used in their amp but says there are separate regulators for the "op amps"....as in more than one. You only need one buffer on the input of the Purifi module....that is what VTV uses in all their versions. The simpler and purer the signal path the more pure the sound. There is also a gain setting pot on the NAD and it is common knowledge that cheap pots are not pure sounding. Look at what serious manufacturers do to make a serious pot. The Sparko labs version of the VTV would have just one better sounding discrete op amp in the signal path in front of the Purifi module. No doubt this version would sound better than the NAD.
Versatility: The NAD has RCA as well as XLR inputs. However, you can simply get a pair of RCA to XLR adapters and plug them into the VTV. You do realize that balanced sounds better. The NAD has a bridging switch. Really, how many people are going to use this? Bridging is best for higher impedance speakers. If you really need to drive low impedance, hard to drive speakers then it is best to use a more powerful amp that is not bridged. VTV makes mono blocks using the NC1200 for that very purpose.
Upgradability: None with the NAD and extreme with the VTV (serious mods by myself.....EVS). My mods can take stock VTV, Nord and Apollon amps to sonic levels that few have ever heard.
So, why would you buy a stock NAD? Some do not know what goes on inside a component so buying from a conservative company like NAD seems safer. Most have never had a component modded so they do not know the value of mods. This is why I will be sending out amps on tour with the mods done so people can really hear what all the TWEAKING fuss is about......you will have your mind blown.