Did any chips go through the bottom end? Or did the piston just scuff and seize? Normally the bottom end will last for more than one top end, if it has been well maintained. If the bearings are all tight, with no slop in the rod bearing and no excessive side clearance at the rod, you can likely put a new top end on it. But you will first want to determine why the top end seized. If you don't and the cause was an air leak (possibly a bad crank seal, or intake leak), your new top end will be toast in very short order. If the saw is generally in good shape and does what you want, rebuilding it is probably worth it, especially if you can do the work yourself.