G'day giannispsaro, welcome to GPS Power.
If i understand you correctly, you want to know if you buy an EU Astro 320 and EU DC40/50s will they work together in Greece. If so, yes the collars will work with Astro 320 they all are original EU stock. If you're asking will a US Astro work with EU collars, or EU Astro work with US collars, then no they won't unmodded. There are existing threads to post in if you have further questions and it would be best to post in them if you do have further questions so I'll close this one.