Did Silo ever come out with modifiers as part of its tools?  $40 sounds good at first, until you consider there is at least one other 3d modeling software out there which has way more tools, including a very powerful modifier system, for absolutely no cost.  I'm speaking of Blender, of course.  With Blender, once you get used to the keyboard shortcuts, you can literally model anything with just your mouse and keyboard, and never have to touch any buttons or menus on the screen.  Plus, you have tons of powerful modifiers, which make it so much easier to bend, twist, taper, or deform any polygon mesh much faster than doing it by hand.

If you really don't wanna learn Blender for whatever reason, there is also a nice little modeling software out there called Hexagon, which can do almost all the things that Silo can do, but for half the price.  I think I saw it at around $20 recently, and it seemed to have a few tools that Silo didn't have, like some modifiers, and I think it might support curves too.