Ahhh... my bad
From what i read it was the other way round.
There are plenty of cheap studio kits available on ebay and such if you don't need the portability. A full kit will set you back a similar to the cost of a 600EX. Note that in due time you'll most likely want to upgrade to something mainstream rather than the china brands. Also with the chinese made ones, take note that Wattage does not truly reflect the output. a 400W china brand may output the same light as a 250W Bowen. It's down to the efficiency of the strobe. Thus the recommendation to save up and go for something better.
You can also pick up a Continuous lighting kit for cheap. $100+ delievered with softboxes and such. It actually helps a lot with getting the shadows right rather than strobe and adjust.
If using 3rd party wireless triggers you'll be fine with any strobe. I have a total of 4 strobes and 2 of them are canons and other than the output power, if used via wireless trigger, it's all the same. Some people strap multiple small flashes together to achieve the same power output ore more than the bigger single flash with faster recycle time to boot! Down side is just that you have to carry more bulk.
600 will trigger the nissin as the nissin has an optical trigger. Might not work very well outdoors in the sun and with longer distances.
It'll be great if you could give us a better understanding of how you'd like to use the strobes, we can give you a better option. You've not answered the main questions of subjects and method of use.