Hi everyone : ) I'm not sure what to study next?!?!?

I have started working in desktop support which I must admit I don't really enjoy. I have passed the Cisco CCNA and in my current role I get to support users with Avaya which is something I find interesting and do enjoy. Thing is I have no real experience other than in my current role as I used to work in Sales. I want to get the CCVP next but worry that I may make myself unhireable as only knowing that field... should I do a server MCTS first or just concentrate on the CCVP and Avaya???? The experience with Avaya I'm getting is pretty minimal, I basically pass on tickets to the network team but I do get involved with bridge calls when there is an outage and the Voice network team have offered to help with equipment, sitting in on training etc as the company I work for uses Cisco and Avaya. But of course I worry if I go for an external job they may not hire me based on that and the CCVP. Basically What I'm saying is I'm worried about putting all my eggs in one basket, it's a lot of studying to get to a point where I can't get a job in the Voice field. Any advice would be greatly received : )