Lab Grade Variac vs Monster Power AVS

In a relatively recent review, can not remember where I read it at the moment, of the Monster AVS2000 Voltage Stabilizer the reviewer commmented that the Monster is a modern version of the age old variac(i.e., voltage regulator) and seemed to be implying why not just use a variac instead. My question is why not buy a large used, lab grade Variac on Ebay or other used electronic source and use it before, for example, the Monster HTS7000 Power Conditioner and save several hundred dollars? Besides the intimidating hype from Monster and others what is wrong with this concept since you will be getting filtering etc after the variac if that is your concern. There may well be a good reason(s) but just want to hear your thoughts. Thanks in advance for your thoughts
The major difference between the Monster and a regular variac, excluding looks and bells and whistles, just talking about performance, is the fact that the Monster constantly adjusts the voltage for you, where the variac stays at whatever position you set it at. IE: if you adjust a variac to produce an even 120v, when your wall voltage is at 113, then when you get voltage fluctuations from the power company, your variac cannot adjust for them by itself. It will maintain a 7v increase, or whatever you have it set for. If your wall voltage increases to 120v, then your variac will be putting out 127v. The Monster will constantly adjust the voltage for you, within a few percent. Monitor your wall voltage. If you have a lot of power fluctuation, a standard variac is not a good idea, because it really won't solve your problem. If your wall voltage is fairly consistent, then a variac could be beneficial to you. Hope this helps!
That is precisely as I thought. I really don't see voltage swings within listening or viewing intervals big enough to justify the Monster AVS-2000 over a large lab grade General Electric Variac that I purchased that has a range of 0-140v and 10-amps (just for some source components after additional filtration/balanced power operation). However, Monster's other high end Power Line product the HPTS-7000 is certainly worth the street price money.