Generally, yes...
I'm not en expert on the science of them, but basically you need a large bass cone to handle the lower frequencies. The smaller speakers just don't cut it.
Any monitors less than a few hundred quid I'd avoid - although there are people on here that'd tell you not to go below a thousand! It all depends on what your budget is really, but monitors are a VERY important investment.
They'll give you years, even decades of service, so choose wisely.
I've got a pair of Event TR8s which are nice. Not the most expensive in the World (I paid around £500 here in the UK) but a good clear, workable sound. A huge leap for me being as I was working with my old hi-fi speakers before!!
Saying that, there are 'budget' monitors around. Try looking at Samson, Behringer, Alesis, ones which I think are quite cheap - although I can't vouch for the quality of them as I've never heard them.
Good luck in your quest...