Experience speaks much louder than certification. If you have the experience, then you can just go to a boot camp to get the certs (and a good employer will pay for that). If you don't have the experience and you go to the camp anyway, you'll either flop right out of the interview, or you'll perform poorly in your job. We're already way overloaded with idjits with MCSEs.
If you like just the networking side of it, I recommend the MCP/MCSA path, with some Cisco thrown in. Hit the networking related Microsoft courses, and then go as far as you can with the Cisco. An MCSE is fine, but being certified on a desktop OS as part of your training is kinda pointless if you're in it for the networking.
Don't discount the Comp-TIA exams. Get them. They're cheap, easy, and they give you an enormous benefit that you might not have considered... They are the prerequisites for the manufacturer certifications. HP, Dell, IBM, whatever, offer certifications on their hardware. They're pretty cheap, they're easy exams, and instead of just being certified on the server's OS, you can also be certified by the manufacturer of the hardware. Since both Dell and HP make a number of popular networking products... With that cert, your company can become a certified provider for the manufacturer. You'll be able to RMA hardware without going through tech support's pointless diagnosis routine. Manufacturer certs are a sneaky one that nobody considers for some reason.
If you want to do security, get crackin'. With that route, the answer to your question is "all of them." A real hotshot security guru needs a whole pile of certifications from pretty much everybody. Microsoft, Cisco, Comp-TIA, and SANS. It's a bitch to get it all, but it pays better than anything else.
