Hey Jeffrey,
I've been researching video cards lately too, since I'm looking to upgrade when I can afford it. I'll try to answer your questions:
Dual displays can mean various things, dual monitors, monitor and TV etc.
As said, you've already decided on the Ti4600, which is an excellent card if you can afford it, but I just wanted to mention that you can get the ATI Radeon 9000 Pro for about half the price of the Geforce 4. it depends what you plan on using the card for: if you plan on using it heavily for gaming, then the Geforce is the best bet, but if you're just doing a lot of photoshop work etc., some gaming but don't need top of the line performance, and also want a dual monitor setup, then I'd recommend the Radeon since you could save a lot by doing that (plus, you could afford a bigger second monitor

)
FYI, here's a comparison of the prices around here anyway:
Geforce 4 Ti4600 128M DDR - $270
Radeon 9000 Pro 128M DDR - $145
I've read the reviews and the 9000 is closer in performance to the Ti4200, but it's still less expensive then even that. (and no, I'm not an ATI salesman

I'm just surprised at how much different the prices are for the fairly small difference in performance between the cards and I thought you might be interested to see that)
For hooking up the dual display system, most (but not all) of the video cards that support dual displays come with the DVI to VGA adapter, and then they should also come with software to configure it.
here's a page that shows what that adapter looks like (and if your card doesnt come with one, most computer stores will have them in stock)
as for a place to research things,
Tom's Hardware Guide is the first place I always look at when I'm trying to find info on any kind of computer hardware.
hope this helps you out!
- David