Aoki's wRC+ was 104, Gordon was 103. You need slugging, but you also need guys who can get on base so they can be driven in. Having someone to be on base in front of Hosmer, Butler and Gordon was something the Royals lineup was severly lacking. Maybe he doesn't fit every team, but he should fit this team well. Kauffman also limits HR, but is positive otherwise offensively, so it really shouldn't hurt his offensive game. Coming to the AL from the NL might.
Also, if you can get Espinosa, and he can replicate his 2011-12 stats, you can get some slug from a non traditional spot.