You can start with pretty much every member of the Top 10!
The difficulty of gaining an advantage against the Berlin Wall, Marshall Attack, and Petroff Defense have caused a huge shift away from 1.e4 at the top level. Anand and Leko were 1.e4 players for years and years before changing.
I recently switched to d4 and basically im looking for some reccomendations for strong D4 players, so I can study how they play it.