Hi!
Welcome to the forumm.
Well, certainly search the archives here since most of your questions/concerns have been addressed many times.
First step to take is to learn all you can about MIDI connections and basics. Also, (while you google for Musical Instruments Digital Interface and learn also don't forget to google some stuff on different synthesis types and a bit of history of synthesis. That's a great start. Without knowing anything about MIDI or different types of MIDI devices and synthesizers things can get very very confusing. I'll leave it up to you to put some effort into learning about what you will undoubtably enjoy using.
Now, as far as gear and options you have. Basically there are two ways to go nowadays.
One is to get some decent software synths and a MIDI controller. You'll have access to different synthesizers right inside your computer. You may or may not have to get a faster PC and some additional things like more RAM, more advanced sequencer/audio software (which you will use as a host application for soft synths). Not knowing what your current computer setup is capable of I cannot be specific. Besides, I'm not really a PC user. I've been using Macs for as long as I remember.
The second option is to expand on the hardware front and get a bunch of good synths. The majic box with sounds in it is called "Sound Module" (that's what you were referring to I believe
), AKA "Rackmount version" or simply "Rack". Most rackmount module synths and workstations have a letter "R" at the end of the model name. 'R" standing for "Rack".
There is no difference between a rackmount and keyboard versions of synths either than one having a keyboard and another basically having everything but it's own Keys. Hence MIDI. As you thought it is very much possible to just take any keyboard and control everything that has MIDI on it. Be it another Keyboard or a module. It's all MIDI. Unless of coarse we're talking early and late 1970's when things were mostly voltage controlled. So instead of MIDI there were CV gates. Not something to really worry about today unless you turn into an analog purist of some sort and decide to use classic analog synthesizers and modular systems. Most of that stuff however is very well emulated digitally and most workstations and software synths of today are quite capable of delivering all the old school sounds. Just telling you a bit about it all. SOmething to google for later.
If you do decide to go hardware (as in oppose to software synths) than there are quite a few workstations that I think you may like. CHeck them out at the stores when you get a chance. If anything, they make awesome KB controllers too.
1. Kurzwell K series. Today's versions are K2600 and K2661. Pretty versatyle. Older K2000 and K25000 are sweet too. Some limitations apply to older versions but that's usually the case with everything. Big advantage about Kurzwell synths is the sound. THey sound great right out of the box without you having to re-program every sound to make it usable.
2. Yamaha Motif, Motif ES and now MO series. Excellent. I use a MOtif ES8 myself and I love it.
3. Roland Phantom. Pretty good too. NIce user interface and some decent sounds too. Although not my number one choice. They sound great by themselves but when mixed with other gear the sound doesn't quite cut through. In any case with a bit of knob tweaking they can be great.
4. Korg Triton series. From Triton LE to Triton Extreme. Some guys hate e'm but I like Korg a lot. Haven't got any up to date Korgs in my studio but won't turn one down if I can. Some complained about the user interface being tough to get used to but I think it's just a load of crap.
Okay, just to let you know all of the above come as rackmount versions as well.
Also, going back to the subject of using software synthesizers I can list a few just so you check out the demos and hear for yourself. I personally use them more than hardware synths. Here are a few of my favorites:
1. NI Absynth 3
2. NI FM7
3. NI Pro 53
4. Ultimate Sound Bank "Ultra Focus".
5. Ilio "Atmosphere"
Google everything I've mentioned. It's the best way to learn. Give yourself some time to explore all the options. No rush. Better to approach the whole thing slowly but wisely and end up buying wisely.
-ED-