Rather than starting with the mic, take a good look (and listen!) to your space. Even if you use the best mic in the world, if your room hasn't been treated it'll sound echoy, harsh, and lack a lot of the bass you're after. Here's a good thread that discusses room treatment in some depth:
voiceacting.boards.net/thread/94/recording-environment-tin-whyMike Delgaudio took a particularly entertaining look at this in this video, in which he turns his shower (one of the worst recording environments on earth) into a temporary sound booth:
www.youtube.com/watch?v=7Wjc_Hv5xAQ(I really like Mike's videos. They range over a whole slew of VA related topics, from gear reviews and comparisons, to building and treating a Whisper Room, to setting up shop in a closet or a car.)
On to your mic question! (There are more experienced heads on this site, so I hope they'll chime in, too.)
There are a couple of routes to go on microphones. One is to get a USB mic. It'll plug into your computer and work with most (if not all) the digital audio workstation software out there. The other is to get an XLR mic and an interface. Same thing: it'll plug into your computer and work with most (if not all) the digital audio workstation software out there. The advantage to going the second route is that once you have an interface you can plug ANY XLR mic into it, even classics that were made back in the 60s and 70s. It offers flexibility. And, of course, there's a good thread here on this topic as well:
voiceacting.boards.net/thread/694/advice-setting-studio-homeThat thread also touches on acoustic room treatment, so it's worth reading the whole thing.
The rest of this you can dig into if you like or skip it if you don't:
One microphone can't work for all situations. I'm relatively new to voice acting, but I've been doing field recording for a while: going out and recording nature sounds as cleanly and clearly as I can. At one point I got a highly rated mic, took it out in the field, and got awful recordings with it. Turns out it was a mic designed specifically for vocals. Problem was, it had a "presence peak" (a high frequency peak in the microphone's response) that coincided with the sound of wind in the treetops. So all my nice, clean recordings were suddenly contaminated by this high frequency hiss that sounded like microphone self-noise. I learned a lesson: Use voice mics for vocals and ambient or foley mics for field recording.
Since trying to get into voice acting I learned another lesson: One microphone can't work for all situations. It sounds like a repeat, but it's not. What it means is that no one mic will work great with everyone's voice. Each voice has its own quirks that are best picked up with particular mics. A mic that works great with female vocals, especially singing, may not work with a male voice. If I remember right this comes up more than once on this thread:
voiceacting.boards.net/thread/185/mic-geeks-favorite-mics-whyAn easy pit to fall into is to say that a mic tailored for female vocals doesn't need a lot of low-end, and a mic tailored for male vocals won't need a lot of high-end. But I think that thread also touches on the fact that both types of voices have resonant frequencies that stretch well above and below what's considered the "range" of each voice. Finding a mic that captures not just your primary frequencies, but the resonances as well, really helps fill in the tonal character of a voice.
When it comes to buying a microphone, I've been told that you shouldn't buy anything you can't try out for yourself first. Which would be great advice, especially considering everything I just wrote, except I live on an island. Unless I fly somewhere else, I can't try out anything first-hand. I don't know how it is for anyone else, but that's just how it is for me. So as much as people say you can't trust manufacturer's spec sheets, often that's all I have to go on.
When you're looking at spec sheets, take a look at the frequency response curve. Ideally you want to see it stretch well into the low-end and not be too wiggly in the high end. A mic that's relatively flat out to 50Hz will pick up lots of the bass you're looking for. One that starts to roll off around 300Hz will sound a lot less "full". Likewise, a mic that has a pronounced peak up around 9-10kHz will sound very bright, whereas one with a shallow peak, say 3-6dB, will pick up the higher registers without overpowering the recording. Even so, you won't really know what a mic sounds like until you hear a recording made from it.
Which is where a whole slew of threads on this site come up. It'll involve a lot of research, but it's good research: Go through the demo reels and clips, and find voices close to yours with recordings you particularly like. See if you can find out what mic they're using. It may not necessarily lead you to a particular mic you can buy (hey, I'd LOVE to post a clip of my voice recorded on a U87... doesn't mean I can afford one). But it'll give you an idea of where to start looking.
Thanks for bearing with my long-winded reply. I ramble.
Tom
P.S. I'm envious of your ability to do female and child voices! I'm thoroughly into gravel-drag territory at this point.