for $50 you can pick up a pair of cheap $25-30 speakers paired with a small budget amp like the lepai 2020 or similar. you can get monoprice new or perhaps a pair of used budget speakers from a slightly better level. other solutions include pc speakers like the z313 or creative a250.
if you can stretch your budget up to around $70 you could get something like the micca mb42, dayton b652 or similar paired with a cheap amplifier like a lepai 2020. pc speaker options like the z333
for $80 solutions like the m-audio av32 can be had. pc speakers like the z523 are available.
for $100 you can get into things like the mackie cr3.
bookshelf speakers targeted towards hifi will sound better than pc speakers but without a subwoofer will lack a bit on the bass side but the front speakers will output a bit more power than pc speakers as well in many cases. pc speakers with a subwoofer may be a bit more boomy sounding but will lack a bit of the quality. honestly any sort of high power subwoofer will cost more than your whole budget. you can add a subwoofer from monoprice later on if you got a hifi speaker setup
if you're on a tight budget, going with headphones is also an option. the koss portapro are bassy and decent for cheap. jvc s500 is bassy for cheap. jvx harx700 is worth looking into. even the audiotechnica m30 is a decent contendor if you can stand shallow earcups.
my suggestions would be:
A) go with headphones in your budget range or make do with a pc speaker system
B) up your budget a bit and get some entry level bookshelf speakers and just be happy with mid bass not low level bass