Softbox/umbrella

Hello,
I almost didn't photographed people till now and now I want to start since I just got a canon 50mm 1.4.

I have a very small softbox that is almost useless and I want to buy a bigger one.
If Ill buy an umbrella, do I need to buy a new head for my tripod?
http://www.ebay.com …ain_0&hash=item​4172126f49
http://www.ebay.com …ories&hash=item​19be3ed25b

And if Ill buy a softbox do I need something to mount it on the flash? Because its really big and im scared that it wont fall off.
http://www.ebay.com …ain_0&hash=item​20cecc3227
I would like a recommendation to a softbox/umbrella at a budjet under 40$, how are those I linked above?

Haven't try myself but heard from many that they just do fine for the price.

As for SB, most important thing to remember is the size. Physics indicates all that make the light soft, is merely the size of source not the kind of material. A small soft box is only good if kept in very close approximate of the subject (Ratio of size of light to subject) and your old one could be helpful if used this way.

I realized that already, but I used the small softbox for macro (very close to the subject)
If only size matters, how more expensive softboxes are better (at the same size)?

Build quality is quite a bit better on the more expensive models I would expect