Microphones produce low signal levels. I pre-amp raises that to a usable (line) level. Pre-amps also provide phantom power to power condenser mics. Different pre-amps will have different features (tubes, phase reversal...etc).
An interface is a device that allows you to record to a computer. It does the analog to digital conversion and connects to your computer via USB or firewire.
Most interfaces have pre-amps in them. The quality depends on the interface itself. If you buy a cheap interface, its likely that the preamps within the interface are cheap.
Depending on the money you want to spend there are different ways to go about a small setup. For rap you don't really need a whole lot. Start with a mic. I don't know anything about the mic that you mentioned. I assume it has an XLR connection. If its a condenser, you will need phantom power. You will need to send that mic signal into a preamp to be able to raise the level to something usable. You can do this with a stand alone preamp, or with an interface with a preamp. If you are using a stand alone preamp you would then send that signal to your interface, which will send the signal to your computer. From your computer you can process and mix the audio and then export it to a cd or whatever you want to do with it.
I personally have an
Mbox 2 mini. It has a mic input with preamp and would work fine for rap. If I had money to invest, I would go out and get a nice tube preamp, but I can't afford to do that. I can still make good recordings without it. The Mbox also comes with ProTools. good software, but really if you are a novice when it comes to recording there is no need to spend that amount of money on an interface and software. You can find an interface that does the same thing with different software for a lot cheaper.
A 2g budget is good to work with. If you only intend on recording vocals for rap then all you need is one mic input. If you want to get into production and things like that you may want a few more inputs.
My mbox 2 mini has the mic input, but also has two 1/4" inputs that I could use for something like a turntable if I needed to record a stereo source like that. Just consider what you want to record now, and possibly in the future.
If I had 2g throw down on a set-up I would buy a good condenser mic. I really like that
Rode NT1a, but with that budget you could spend more and get better. I'd probably then go to something from the MBox line. I'm familiar with protools, its what I was trained on so I like to stick with it, but if I found a better deal I'd go with something else. The main point is having enough inputs for your needs. Then I would look into a nice preamp, probably with a tube to add a bit of warmth. The Mbox would have a preamps so adding another wouldn't have to happen, but if you can afford to upgrade a preamp, it wouldn't hurt. After that I'd look into a good set of monitors. After that it would depend on the results I'm getting with everything. Maybe you could get some beat making software, or samplers or something. Maybe some acoustic treatment would be good, or take some of that money and build a better vocal booth or area to record.
