I record in a room that is far from quiet. Computer fan noise, traffic outside (far away though, 400' or so), and although it's annoying, I wouldn't let that discourage you from buying an LD mic. If your recording on a computer, you can edit out a good chunk of the noise, during parts that nothing is happening. Sure the noise still exists when the vocal, acoustic guitar, whatever kicks in, but it's not the end of the world. At least not for my purposes, maybe yours to. If your doing drums they will drown out any computer fan noise, sure the noise is still there, but. Some of your recorded instruments may be direct, you didn't say. I was listening to some Zep last night, the tape hiss is more noticable on those recordings than the computer fan noise in my far from quiet recording room.
So, give it a whirl. I wouldn't let that be the number one factor in a mic choice. Style of music and the song itself would be a good consideration as far as acceptable background noise.