We've spoken with (and worked with) some of the top mix engineers in the world and it's clear that studio gear comes second to experience and a great ear.
There are lots of microphones that are low maintenance compared to a Neuman and just as good. The Rode NT2 did us fine for years and sounds great, for example. Despite what a lot of people say, the human voice is a very simple sound to record - there are no transients and it doesn't have a massive bandwidth - just take a listen to the TV; they use a basic little mic attached to peoples lapels and the voice quality sounds fine.
That aside, if you download an acapella from a famous song you will hear that (typically) it sounds very thin. This is because vocals are EQ'd away from the natural sound of the mic to fit the music. Mixing a song very often means we have to make the whole song "fit" and natural frequencies of each component of a song get moved about a lot.
A mic preamp is a very simple device and so long as it doesn't clip easily and is not adding noise, you'll find most modern desk pre-amps are perfectly fine.
It is not so much about the mic but more about the sound source - if the voice sounds good it will sound good on most mics. Once recorded it is down to what you do to it that makes it sound good in the track i.e compression, eq and effects. A good plugin to bring out the high frequencies without boosting the top is the BBE Sonic Maximiser.
And, for the biggest shock of all; 16 bit 44.1 is absolutely fine. All you get with higher bit rates is bigger files - the sound is just the same. It's all about what you do to the mix!
The real truth is that in order to get very professional sounding songs, you need to work with very professional producers!