A silk (diffusion screen) is an excellent tool, and is often used in conjuction with a softbox, to effectively make the softbox much bigger, but it can be an awkward tool to use. A 60x60cm softbox is a bit limited for many still life subjects, you really need something bigger - this particular subject is just about OK, but if it was more shiny you'd need a much bigger one. As Steve says, your softbox isn't close enough.
Your biggest single problem is light placement. For this type of shot you NEED a boom arm because the softbox needs to be directly above - there is no alternative.
It also needs to be angled forwards a bit, which it isn't in your shots. This would (with this particular subject) light the top and most of the front elevation but would leave the vertical bit at the top and parts of the handle unlit. A simple reflector would then push enough light back into those areas. The reflector probably needs to be white, or maybe light grey - don't use a silver one for this as it would create unwanted reflections (putting the light where I suggest would avoid those reflections).
You've got 2 flash heads, but that doesn't mean that you need to use both on every shot - this is a single light shot!
For a subject as simple as this, just use a black background and cut it out in PS. That way, you'll be able to choose a suitable background later. More importantly, you can have a white (or any other) background without light from it bouncing around and ruining the shot.
I totally respect the fact that you've posted these shots SOOC - this is what everyone should do, so that we can see the actual shot. But, once you've got a usable shot you will need to adjust luminance and contrast to get the best from the shot, and a bit of usm works wonders too.
Seriously, do look at one or both of those books. And the Photigy tuition is extremely good though will cost a few quid every month but you can drop in and out of subscription.
They also have a facebook group worth a look at
https://www.facebook.com/groups/photigy/ some really good product photographers use these resources, though do be prepared for some serious but constructive critique if you post an image and if you do you will need to post a 'Behind The Scenes' image to go with it to show the setup you used. Which actually wouldn't be a bad idea here.
I can't comment on the paid subscription service but I do belong to the FB group and some of the advice there is sound. Some of it though (other FB users) is hopeless, it's just like a forum, with a wide quality mix.
EDIT: I meant to say that bringing the sofbox closer effectively makes it bigger relative to the size of the subject. But, because of the way that the inverse square law works, when it's really close the power of the light will fall off very rapidly as it travels down the subject, resulting in over exposure at the top and/or under exposure at the bottom - and cosine law doesn't help with this either....
So, the best answer (which may be out of budget for you) is to have a much bigger softbox a little further away.
