By swappable I mean when replacing a transfer switch must it be exactly the same model as the old one? For example, as it looks like we'll have to go that route we presently have a Surge Guard Model 40250. Price for this particular switch seem to be over $600. Other search results show switches that look similar but have a different model number are are much less expensive. Are all transfer switches created equal or is there a compelling reason to stick with the same model? Possibly consider a different, better model?