You have to be careful with adjectives (and their associated o-forms) when they are prefixed with не-. Some such words have a pejorative meaning, correlating with English un-, e.g. неприїтный 'unpleasant' and others have a more positive connotation, like небольшћй 'not too large, rather small, modest.' To be safe, consult the dictionary.
The word небольшћй is a good word to use in order to avoid the pejorative connotations of its near synonym мђленький 'little'. Compare:
Ћн живёт в мђленьком дћме зђ городом. He lives in a little house outside of town.
(The poor guy!)
Ћн живёт в небольшћм дћме зђ городом. He lives in a modest house outside of town.
(It's a nice place. Not too big, but nice.)
Thus, some adjectives with не- are not truly negative, at least not in their connotation. The true negative particle не is written with a space:
Егћ дћм не большћй, а мђленький. His house is not big, but little.
У негћ небольшћй дћм зђ городом. He has a modest home outside of town.
Here are 4 words to evaluate prices, listed from cheap to dear. Note that English words such as 'pretty, not too, rather' render this meaning of не fairly well:
Јто дёшево. Јто недћрого. Јто недёшево. Јто дћрого.
That's cheap. That's reasonable. That's pretty expensive. That's expensive.
  That's not too bad. That's not too cheap.  
Here are the o-forms of two words you know (плћхо and хорошћ), with and without the 'nice' prefix не-:
Јто плћхо. Јто нехорошћ. Јто неплћхо. Јто хорошћ.
That's bad. That's rather bad. That's rather good. That's good.
  That's not too good. That's not too bad.