I presume the price you quote for the 420 above includes the software necessary for it. I have a personal system and don't need anything fancy at all in regards to software. I found that really stupid, particularly with the increase of 2nd lines in homes for modems. I had to do a work around to let my modem use my 2nd phone line AND go through the other surge protector. And it really means nothing as far as measuring protection.
Voltage sags can cause damage over a longer time frame than a surge.
Sutton Designs has been around since 1972. We produced some of the first small UPS models and some of the first surge suppression products. We have been making Power Protection products longer than most others have been in business. You will come across our product in virtually every corporation today. The street price is the list price.