The fun of working on your bike rebuilding it just like you want is well....part of the fun.  But it is the more expensive route.  Finding a bike that is a high dollar build and totally restored would be far far far less expensive to buy when they come up for sale than building it and buying all those components yourself.  It comes down to what is it worth to you to have the enjoyment of building it up yourself...and how long can you wait to find the cherry quad you want..