In recent years I have become a 100% user of Paul C Buff lighting products,
http://www.paulcbuff.com best known for Alien Bees and more recently the extraordinary Einstein mono lights. I have eight of them. Because you're buying direct from the manufacturer, prices are startlingly low. In my busy business which is mostly on location, the Einsteins, stands, triggers and modifiers have passed the "tough-test".
This is after a very long time with supposedly superior Profoto lighting equipment which I had a lot of, mainly 600 Compact heads and a couple of 2400 w/s floorpacks for serious grunt. It's all sold now, the efficient, lightweight and breathtakingly inexpensive Einsteins do all the heavy lifting now. I think an Einstein costs less than a new 600EX-RT.
Modifiers, softboxes etc when used with speedlights is OK up to a point, but the necessarily low w/s output of a speedlight means that only short duration, small projects can be undertaken. When you get a flow going with a human subject, waiting for flash recycling after full power dumps, and running your batteries down after not too many pops is plain unprofessional and stunts the creative flow in a shoot.
-PW