18" from the front of the speaker or the back? Proximity to the wall generally impacts bass response. Some speakers are more sensitive to placement than others. Some speakers are designed for near wall placement, and others benefit from being further in the room.
(I prefer the smaller speakers I own farther from the wall on stands.)
A couple of things you may want to consider:
Box speakers come in ported and sealed designs. Some may fit your needs better than others regarding your placement options. There are articles/posts online that explain the difference, etc.
The other issue is power. Different speaker designs require different amounts of power to get the most from them. For example, if you know you are buying a 10wpc amplifier, I'd buy speakers with that in mind. Some 'bookshelf' speakers are not efficient enough to be driven well by 10wpc. On the other hand, you won't need a ton of power for efficient speakers. You can sometimes meet the minimum power requirement listed for speakers, and although they sound good you will not get the best of them.
It's not good vs bad- just different. The thing that matters most is that you're happy with your gear/music.
Hope this helps