The lighting in the test shots is very flat. There’s nothing TECHNICALLY wrong with flat lighting other than the fact that it’s un-interesting. Instead of blasting all the shadows away, try to use shadows (rembrandt, loupe, butterfly …).
While there is nothing wrong with that type of shot, you DID place your subject too close to the wall … notice the shadows on the wall on the first image.
Back to light setups … it will depend on what type of shot you are trying to do of course so I’ll start with the pure white background, highkey type shot.
For this type of shot, you’ll want to use your 2 softboxes AND your speedlight.
Aim your two softboxes at the wall (one softbox on each side of the subject) and set your exposure to OVER expose that shot until you clip your highlights … this will make the background pure white. Then use your speedlight to fill in your subject. You’ll need to have your subject OUTSIDE the area lit by the softboxes (so closer to you than the softboxes themselves as you don;t want any of that light directly on your subject.
Another type of shot would be one main light and a kicker.
Something like this: http://flic.kr/p/dvgvK1
Notice the main light coming in from the front right of the subject and the light hitting her arm from the left of the frame?
There are a tons of other types of shots you could do. You also don;t HAVE to use 2 lights …
This was shot with one 85W (300W equivalent) CFL bulb and a reflector set as a diffusion panel:
demo shot: http://flic.kr/p/dmniKe
setup shot: http://flic.kr/p/dmnhJ6
You could do something similar with your softbox.
Good luck and have fun experimenting.