My honest opinion is that if your budget is $400 and you want something decent you're going to have to go with a used saw. Look at the table saw chapter in Mark Duginske's book, Mastering Woodworking Machines, and then go shopping for a used contractor's saw on Craig's List. With patience and careful shopping you should be able to get something for under $400, maybe even far enough under $400 to buy a mobile base for it.
My experience with the portable table saws is limited, but I have successfully used the Makita, DeWalt, and Bosch saws. If you could find one that has been hardly used at all, and you limit yourself to wood no thicker than 1" hardwood or 1-1/2" softwood, one of those might be fine. I have no idea how well they age, and if anything broke or wore out I wouldn't expect to be able to repair it. The portable saws will all feel flimsy if you ever try out a decent cabinet saw. That doesn't mean nobody should have a portable saw - - but using a big, solid saw would give you good perspective on how much coddling and coaxing it takes to get decent results from the portable saws without breaking them.