What cert is best to learn network support?

I am a former PC/LAN Tech with four years’ experience who has taken a job as Network Admin. Mine is a one-man shop supporting 3 servers (soon to be 4) and 12 workstations.

My question is this: What is the best certification to enhance my knowledge of networking and servers? I’ve considered Network+ and the CCNA, but not sure which one is best to enhance my knowledge base. (I know that usually the knowledge precedes the cert, but I am the type of ‘student’ who can learn from a book and put it into practice.)

Oh yeah, I already have the A+.