Is there any particular reason you want to do this in hardware? Is it important for you to do this live?
I produce my music almost exclusively with software, and you'd be hard pressed to find an argument that would convince me to go in any other direction. All the hardware you need is a computer, a MIDI (USB) keyboard, and maybe an audio interface if you want to use microphones.
The argument for software is that there is an astounding array of synthesizers, samplers, drum machines, and FX out there, and you can get them all in one box. They are also cheap, and require no physical maintenance. It also gives you (along with a DAW) ultimate control over alll parameters, with envelopes and sequencing, etc.
The argument against, is that you have to use your keyboard and mouse (mainly the mouse) to interact with them. For me, it's a no brainer. If you absolutely need a knob or something to interact with during a live show, you can buy a MIDI controller that has some, and configure them yourself.
The argument for hardware is that you get a single purpose unit, which has been tailor made for the task it's supposed to perform, ideally giving you a better user interface, since it offers custom buttons, etc. I find this to be inspiring to work with, and it also feels more immediate, as if I'm more in touch with the instrument. However, the difficulty in controlling the parameters from the DAW, MIDI delay, as well as only being able to get one sound at a time from each unit always keeps me from actually using hardware much at all. It's for people who don't mind investing a lot of money.
For making a full electronic music production, the user interface you get from a modern DAW like Ableton Live is probably going to blow any hardware sequencer out of the water, too.
I don't know exactly what you want to accomplish, so it's hard to give any very specific advice, but no matter which route you end up going, you probably want to get a DAW. Personally I'm very happy with Ableton Live. I think it's perfect for electronic music, but it may be slightly hard to use if you're completely inexperienced with studios or DAWs, although I think it's nothing that you shouldn't be able to get through with some tutorials. Some other candidates are:
NOTE: If you don't have, and don't want to buy, and audio interface, get asio4all! It's an audio driver which allows for minimal output delay from DAWs. This is if you use a PC, apparently it's not necessary for Mac.
For synthesizers, etc, look up VSTs if you don't know what that is. Basically software audio plug ins. There are a bunch of pretty nice free ones out there if you care to keep it legit:
mellowsound (mellotron VST)
tb tapeworm (mellotron)
Basic 64 (chiptune VST)
Magical 8-bit plug (chiptune VST, very easy to use)
If you're just starting out, and want to see what's out there, you could just pirate a bunch of stuff and see what you like. I'm happy to give you some more pointers if you want to know something more specific.