YN650+580ex+7D?

I'm considering buying 2 YN650 flash to partner with my 580exi and a 7D. Will these work together? And will I need to buy a radio trigger as well to fire all 3 of these or will the pop up flash be adequete? Thanks.

Yn650? I'm assuming you mean the yn560 as there is no yn650.

The yn560 is a manual only flash. It doesn't not do ETTL. But yes, as long you you are looking to do manual and not ETTL, it will work with the 580ex and can be triggered with your pop up flash (again only in manual mode).

If you're looking for a flash that can do ETTL and/or wireless ETTL then there are several other yongnuo options like the yn565ex, yn568ex and the yn560ex (formerly the yn600ex). The yn560ex is different from the yn560 (notice no "ex" at the end) in the fact that on camera, like the yn560, it is manual only but off camera, unlike the yn560, it can do wireless ETTL.

Thanks Gremlin. I'm on a fairly tight budget hence the reason I was looking to the YN560 (lol not 650)

After reading your post and a bit further research I'm thinking it might be worth my while pushing my budget a bit further and buying 2 YN560EX.