Depends on where you want to spend your time. If you like making stuff for your shop you could build your own. If you like making stuff for your house then just buy a good commercial offering. Welded is better than bolted together. HTC makes some good stuff. I also like the big wheels on the one Steve mentioned. Note that it goes on sale regularly for ~150$.
Good luck!
Salem
As Joe mentioned, I have this one under my TS and jointer and they have worked extremely well, Just cut a piece of 3/4" plywood and attach the wheels/casters and the gear ilfts/rolls well!:icon_thum
FWIW, Steel City manufactures and sells a mobile base for their cabinet saws. The sell the cabinet-only mobile base for 30" rails, or the cabinet plus table extension mobile base for 52" rails.
I have an older 1-3/4HP Steel City hybrid saw with the Steel City mobile base and have no complaints. I ordered it with my saw but it can also be ordered seperately.
I build mobile bases for most of equipment. A piece of 3/4" plywood for the bottom, sized to fit and a 2x2 frame to hold the tool in then large locking catsers on the bottom. 3" locking casters are at Woodcraft for about $10 each but you can sometimes find them on sale.