580ex with 550ex compatible?

I currently own two 550ex speedlights and an ST-E2 and am looking to expand my system. I use a 5D and a 1dMkII.

My question is, if I buy a 580ex, will this be compatible with the 550's in a wireless set-up. ie will the 580 as on camera master properly fire the 550's, maintaining E-ttl? And will the ST-E2 fire both 50's and 80's with full E-ttl?

Another possibility is 430's. Would they intergrate in a system that includes 50's?

I don't want the expense and hassle of selling the 550's and replacing them outright with 580's

Any help and explanations would be much appreciated.