depends on your preferences honestly. both speakers and headphones have good and bad points. if you want a decent 5.1 i'd spend a bit more than your headphone budget though as what you will get for around $100-200 is generally only average at best for 5.1 and headphones will be better.
what will sound GREAT for that budget?
headphones (dt770, dt990, etc)
2.0 powered speakers (mackie cr3/cr4, m-audio av30/av40, micca pb42x, etc)
2.0 passive speakers + amp (pioneer bs22, micca mb42x, etc)
what will sound acceptable?
5.1 pc speakers or similar (logitech z906 or similar creative sets)
if you want something "good" for entry level 5.1 home theater i'd suggest at least around $450-500 to work with. you can get a sony 5.2 receiver for $170 or so and the energy take classic 5.1 take or copycat monoprice 10565 for $300 or so (or klipsch hd theater for similar price). that a decent setup for on the cheap that you should be happy with. there are speaker sets for around $200 you could use as well but its worth spending the little extra.
that what i do myself.. pictures in signature.. i have a receiver and 5.1 setup hooked up to pc and ps3. its GREAT and i wont trade it. i do have headphones but honestly headphones lack the freedom of movement you have with speakers.
if you plan to record video and talk into a mic.. you want headphones or have your speakers muted or low while you do.