Weak signal with condenser mic

Hi, I have been in an eternal downward spiral for several weeks trying to update my audio set up. I finally got everything in working order but I'm having problems getting a good signal with my Samson condenser mic. I am currently wanting to record some acoustic guitar and would like to reduce the amount of white noise at least by half. I purchased a Yamaha USB mixer and found the mic pres to be kind of weak so I took someones word for it and purchased a Firebox by Presonus thinking that it would do the trick. I'm still having a problem getting good levels. In order to get the audio to a sufficient level I need to crank the gain up to a max of +30, hardly reasonable as it causes a tremendous amount of white noise. Also, if I'm more than 6 inches from the mic with the gain maxed my signal doesn't even come close to hitting the yellow unless I yelp at a high enough volume.

I'm running Logic 8.0.1 on a 1.8 ghz G5 with 2.5 gb of ram. I'm switching between the Yamaha USB mixer and Firebox recording interface. I have tried buying better quality mic cables, isolating my acoustic guitar a good distance from my Mac, putting gates on my channel strips, moving the mic around to different positions, etc. I'm wondering if maybe it's my mic and if so how can I check that? Any recommendations are very appreciated.