Wrestling + Boxing is probably a better combo. Most wrestlers prefer boxing over kickboxing because they don't have to leave their base and compromise takedown defense. Examples of the style in action: Mark Munoz, BJ Penn, Brock Lesnar, Rampage. They don't throw many kicks; they box in the standup and use wrestling for TD defense or actively taking the other guy down.
Muay thai + BJJ seems to work well together as well. Examples include: Shogun, Jose Aldo, pretty much anybody thats ever fought for Chute Boxe, and others I can't think of right now. They let their hands and feet fly with little worry for being taken down.
But with the wrestling level being so high in MMA, I think most people are shifting towards wrestling now which naturally moves them into boxing rather than kickboxing.
But nothings set in stone, there are plenty of sick fighters who mix up every style.