then tell us more about it
what midi-controller and software do you use??
what sort of music do you make?
if we know these answers we can see what fits you better (or actually we can give advice and YOU'll see what fits you better
) or what you'll need..
to be honest 150-300 is not very much if you don't have much equipment yet..
when working with computers you still need a GOOD soundcard, a pair of good monitors (the sound on pc-speakers isn't "real" enough to do any working or mixing on it.. once you'll hear the difference you know what i'm talking about)
but what you could (and actually should) do.. and most people here do it this way: get one piece of good equipment after another until you have everything you need..
of course for larger investments you should have your mind already set-up that you're willing to put money and effort into this issue (if you haven't already decided
)
so give us a list of your equipment (maybe also the specs of your computer) and then it's probably easier for us to be able to help you..