As the title says, if I wanted to really get to grips with a non-Silver Age/insane acts (ie lassoing the sun) Wonder Woman power set, am I good for reading the new-52 or do I need to look at earlier work?

Start better with post crisis, the George Perez run right after Crisis on Infinite Earths.

I will, thanks.

No problemo, but don't forget the related specials and most importantly the annuals.

The New 52 series by Azzarello is not very good place to look for demonstrations of what Diana can do, since neither Azzarello or his chief artist were your standard superhero-comic creators.

I would recommend the first Rucka run, since he was one of her creators most into establishing what Diana can do physically compared to other characters.