Anouthe bit of software worth a look is Ableton. You get a lite version of it for free.
If you’re doing this just to chuck ideas down, then just use your hifi to play through. If you’re going to be making demos or producing music, then a set of studio headphones, monitors or both.
For headphones, superlux 688b are great value, though after 3 years my plug has become iffy (but they were only £30).