great advice.

If you're thinking of getting an SM58, you might be better off with a 57.  I think it has a bit more utility (although you said you would use it for vocals only) but it is essential the same mic.  Or, if you already have a 57, try it on vocals and see how it sounds, it should give you a representative picture of what a 58 would sound like.

I too have been thinking of a different mic, mic preamps, etc.  To get into recording, just a couple of years ago now, I bought a decent entry level condenser mic, an AT2020.  Last year I upgraded to a Quad-Capture from a Fast Track Pro interface.
 
I've recorded my vocal(s) in my untreated spare room studio, but I've never pushed the mic or experimented really to find the 'best' sound...until yesterday.
 
After watching some videos on mic techniques, asking questions about preamps and so on, I'm finding that singing into the mic from farther away and about 45 degrees off of center, no screen, combined with fine tuning parameters on the Quad-Capture's control panel is yielding the best tone, sound, nuances.  I'm a baritone too, with a fairly smooth style, if you will, and the off-axis position brings out more edge, grit, highs, maybe?  Singing harmonies might be best in front of the mic.
 
If you're set on a new mic, go for it!  But, I discovered that the mic I already own is just fine, for now:)
 
 
 
 
 

So bought a new mic and will be buying 2 other mics soon.  tested some and looked at all prices availability etc.
 
Have a AKG C1000S
 
Bought a Blue Microphone Baby Bottle - got it for $310 with some dealing.
 
gunna get a Shure SM58 and a Rode NT-1A Kit later on to have some other vocal mics to play with.
 
That will give me 4 decent/good vocal mics to play with and really get experienced with.  if later on I need something much better then I can try more expensive mics.
 
thought I would provide some follow up to the discussion.  thanks for all the assistance, it gave me a lot of thought and I was able to talk to some people in person at stores and didn't sound like a dork.

They're a little more than $300, but I've been using MD 421's on vocals for a while, they sound really good and you're not going to get much better for less than 2K. Personally I think they sound better than mics that are a lot more expensive.
 

While choosing your next mics this may come in handy: http://www.prostudioreviews.com/mic-graph.html
 
Rocky

I have two condenser mics in the under $300 category.  An Audio Technica AT2035 and an Audio Technica AT2050.  They are very similar except the 2050 can be switched to omini, cardioid or figure 8.
 
I've been using the AT2035 for over a year, for vocals.  I wanted a second and went with the 2050 since it has the switchable patterns. 
 
 

Seem my AudioTechica has been unavailable for a longtime, which is a shame as I would like the option of a matched pair for stereo capabilities If I was going for a single condenser now I'd make sure it would be one where I could pretty much count on finding a match for it later.
 
 

I have a large number of mics, all of which have been retired in favor of the CAD Equitek E100S... just exquisite, lowest noise of any mic, built right here in the USA...
 
I'm a singer.  love it.
sound on sound review:  http://www.soundonsound.c.../articles/cade100s.htm
 
Their conclusion:  
The E100S is a very different beast from its earlier namesake, but its ability to serve as a reliable all‑rounder makes it a must‑hear mic if you're thinking of a spending spree this Christmas. Its smooth but detailed sound character is quite ribbon‑like in some ways, and provides a perfect antidote for those who find the shrill brilliance of many modern capacitor mics too much in combination with squeaky‑clean digital recording systems. The E100S is a remarkably quiet mic, with a full-bodied and detailed sound and an ability to cope with silly sound levels. There's nothing in my mic collection that sounds quite like this, or is as universally useful as this mic. For that reason, this one is definitely staying here! .

Alternatives

Given the E100's remarkably low self‑noise, its integrated 'stealth' shockmount, and its detailed but smooth sound character, I'd struggle to think of anything that really compares, let alone compares at a similar price.

I have the Rode NT2-A Mic.....
 
I love that mic....it is rich and warm for me and I have a crappy voice....
I have a blue tube pre amp which was not very expensive but for me....it works well so I am happy with it.