The YongNuo flashes are pretty nice and cheap but they only have a GN of 33 for models like the 468:
If you want a higher GN (guide number / power) you will want to look at the yn 560 (there is also a 565 that is supposed to be coming out that will have ettl ability as well but not everyone is carrying it just yet.)
The YN-468 goes for right about 100.00 on most sites, here is a link to amazon:
http://www.amazon.com …9&creativeASIN=B003LB0DAM
They have a few options for getting it plus they are a pretty secure way to buy IMO.
the YN-560 which has a heck of a lot more power is here:
http://www.amazon.com …9&creativeASIN=B004GZLFHM
It's cheaper at only 70.00 but it doesn't have ettl, so you will only be able to manual. If you are using it for off camera flash, then by all means, tear it up, it's a great flash, I was recently using one that a friend had bought and he loves it. I loved how easy it was to get this sucker to working and controls were easy to work with. I want to get one for myself to keep for that extra power when needed.
I have a Canon 430ex II and I find that the power is a bit low for my purposes but then again for a flash like the 468 that is that cheap you can't really go wrong with it... It's cheap, gets the job done and will keep you happy for a long time. also later if you want to go crazy with flashes you can always use the 468 for fill light or separation light, whatever you want to use it for you can and it'll always be that great cheaper flash that you got for next to nothing that still performs.
I have an older YN flash that I use only in manual mode and it's always worked great for me. It continues to perform and hasn't given up the ghost on me yet. Even if it does, I wont really care because I've had it for a couple years now and truly beat the hell out of it.... I don't often beat up my gear but this unit has been through some mess. Most likely because it's cheap, i'm not too worried about it getting scratched up like I am with all my other gear.