I have a 650. Which is a monster. But if you're not travelling with it, You may as well get an old long crosscut saw. Much cheaper.
The silky files though are brilliant for everything. Big iron filings come off, when you use one on an axe. In the silky saw instructions, it tells you to file each tooth exactly 79 times!
A couple of guys in Canada Bob and I were with were using them, [which is why I wanted one] and the speed which they cut through big cedar trunks was amazing. Almost chainsaw fast. You dont have to apply much force, it cuts on the backstroke.