Scott, the biggest reason for the riser block is to allow resawing of thick material. If you have a 1x8 that you want to make into 1/4" thick pieces, you may not be able to get the 7-1/4" dimension into the throat of the standard saw. With the riser block, you can.
You may not think that you would ever want to split a 1x8 but there may be many directions that you can go in woodworking and I think that you would be a lot better off to have that capacity now than go back years from now and try to find a kit. Other things that require the higher opening include making "natural" wood furniture where the round wood has never been sawed flat, sawing small pieces of highly figured or highly desired specialty wood from round to flat, sawing large blocks for turning on a lathe and something that I haven't mentioned that you WILL want to do someday and you will cuss yourself out for later for not getting the block but I don't know what that will be either.