Thoughts on using a 580EX II or a 550EX with a 600-EX?

I'm pretty new to flash lighting, and I am using a 5DM3 and a 600-EX for portraits, along with PocketWizards to wirelessly trigger the flash. Someone wants to sell me real cheap a 580EX II and a 550EX.

1. Can either of these flash units be put into slave mode to act as a second light? If not, is there a way to trigger them as a second light?
2. Any thoughts in general on using either of these two flashes along with my 600-EX as a second light?
3. Will PocketWizards work with either of the two lights to trigger them?

Thanks.

Both can be used if your 600 is set to optical master (vs. radio)

The 580EXII will add a number of features and groupings that the 550 lacks, and the interface will be more like the 600, but you should still be able to use the 550 as slave no problem.

No need for PWs.

Sorry, got a bit confused...
1. I use Pocket Wizards with my 5DM3 and the 600-EX. Are you saying I do not need to use PocketWizards to wirelessly trigger the 600-EX?
2. Can both be used at the same time with the 600-EX?

Thanks.

The short answer is that if you’re used to using the pocket wizards, just put the new flash on one and extend your options.

The more complicated answer is around the 600ex having its own receiver built in, you just need a compatible transmitter for it, you can sell the pocketwizards and extend your options.

Do you have the 600 EX-RT? If so, Invest in the Canon ST-E3 RT Transmitter. Don't buy the other non radio based flashes like the 580 EX-RT or 550 EX. Why not take advantage of the Radio Based 600 EX-RT?

Just feel I should mention that the 550EX doesn't have a PC sync port. If your PW triggers require cabling to a sync port, you'll need to add a sync adapter to the foot of the 550EX.

True, and here's the adapter I use:

The 600RT has an optical mode to trigger the non RT type flashes. They work well for line of sight but may not reliably trigger if there is some blockage. Have to make sure the transmitter is going to be able to be seen by the receiving units receptor. The 600RT will be able to control those flash units to so that is a really nice aspect in multi flash instances and grouping them.

I use a 600RT-II with a 580EX frequently but with a radio trigger system. My other suggestion may be to pick up and 430 EX RT unit at ~$200 (refurbished) to expand on your 600RT and have a compatible Canon RT system. The optical works well just that it is aging tech and the radio trigger is easier IMO.