Hey,
Let's look at the things you'll need to buy for each scenario:
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Rack Sampler=$1000 for a nice one with lots of RAM and lots of hard drive space.
Sequencer program=$250 for a nice one with lots of MIDI functionality.
Keyboard controller=$120 ish, you'll need this to play your stuff.
MIDI interface=$50, you'll need this to connect your sampler and your keyboard to your computer.
I would also suggest getting a small mixer, it makes it very easy to connect the output of your computer and sampler, plus whatever else you may get in the future, and send it to your speakers.
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If you get an 'all in one package', you will need this:
All In One package: $1500 for one that samples, it won't be as powerful as a rackmount sampler, but it does have a sequencer and a data entry device (keypads).
You won't need your computer to make music right now if you have an external box, but you will need one eventually to:
1. Do any serious editing of the audio and midi files.
2. Put your stuff out on cd or mp3.
3. Get more gear and want to have everything to work together.
4. Want to mix audio and MIDI tracks.
5. Want to take advantage of a big 19" monitor instead of a 1" LCD.
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There are still some options for you with soundcards, a lot of manufacturers have made special cards which plug into your USB ports and they sound really good. Many of them have MIDI interfaces built into them, so you'll have some MIDI ports if you ever need them. Here's a couple from Midiman:
http://www.midiman.com/products/m-audio/USBaudio.php
YES!!!! It makes a HUGE difference in day to day use. A computer is not a portable as a box and you won't get the 'cool' factor that goes with having a box, you will have to learn software and hardware which can be significantly more complex than a box is to learn, and you will have to enter your notes on a keyboard instead of on a drum pad...
However, computers are WAY more powerful than boxes and they can be expanded more cheaply. I'm speaking from experience; once I got into using a computer I couldn't believe how limited the box was, I was easily able to do things on the computer that would have taken ages or been impossible to do on a box.
Take care,
Nick
