My general rule of thumb is use whatever works. I've cut tracks for mixtapes where I've literally just handed the dude a cheap little Audio Technica and the vocals came out pretty decently. I don't have a mic closet per se, but I have a few dynamics and few condensers to choose from. I've had success with condensers on Hip Hop artists, so I won't personally say it's not the way to go. However, some really great sounding vocals have been cut with dynamics, so the belief in condensers being the "sure shot" is somewhat misplaced.
My advice is to at least get one dynamic and one condenser in your life (so in your case keep your AKG and get a dynamic, be it an SM58, SM7, etc), try them out on each vocalist you work with and choose from there.
Peace