Originally Posted by gorbishganoid
For my synth I want to be able to do stuff like make beats used in hip hop music as well as like the stuff used in trance music.
With a $700 budget I'd say to get a 'dumb' keyboard controller to connect to your computer via USB, choose digital audio workstation (DAW) software for recording, editing and playing back digital audio, then choosing bang-for-the-buck software synths and drums/drumsynths and/or sampler and do everything from your computer. On PCs a lot of people starting to make beats use (and even stay with) FL Studio
Look at 49-key and 61-key controllers (with full-size keys) from Akai, M-Audio and Novation, different models range from $150 to $550, and some models come with 'lite' versions of popular DAW software.
Tweakheadz is a great introductory guide to musicmaking and home studio equipment. Spend an hour or two here: Tweak's Guide to the Home and Project Studio