Eddie,

FIRST, EQ the low end out of your vocals. High pass them at 80-150 Hz, adjusting the cutoff frequency to taste.

Then use compression to make the quiet parts louder as rharv suggests. No need to burden the compressor with unusable and unimportant frequency content.

Your method is not recording stereo. Stereo means there are definite signal differences in the two different channels. Simply copying one channel to another doesn't do this, and doesn't provide the cues your hearing system uses to say 'that's a multi-dimensioned sound'.

Your method is still mono, just a summed mono approach. Shouldn't need to do this. Turn your other tracks down.

Recording mono is standard practice for ANY source that is 'small sized' in terms of where the sound comes from. Example: Trumpet, saxophone, most wind and brass instruments for that matter.

When you listen to a solo trumpet standing at a safe distance - does it sound wide, or can you point directly to where the trumpet is? You can point directly to it, unless it's in a reflective environment.

Now, contrast that with a 'wide' instrument, like a piano. If you are playing the piano, you hear low notes coming from one part of the piano, and high notes coming from a different part. It begs for more than a simple mono recording technique.

When you hear a solo singer, you do not hear them coming from more than one location - but a point location. Ideally suited for a mono, point-source recording technique.

Look at any studio photo you want to look at where a solo vocalist is being recorded. I'll make it easy for you. copy/paste this into Google "recording studio vocals" and click the images link.

99% of the time, the pros are using a single mic to capture the sound. Sometimes, they might put up a few different mics, but this is not to make the sound stereo, but to take advantage of the coloration that the different mics put on the recorded signal so that they can decide after the fact, which mono recording they will use to dominate the sound, and which mono recording they might bring in underneath for support.

Contrast that with 'wide' instruments. You'll see an x-y pattern, or blumlein, or M/S or other stereo micing technique being used to capture the width of the source. Type this into the google image search and you'll see all kinds of stereo and more mic techniques "recording grand piano mic placement" .

The big pro to recording in mono for mono sources, is the file size is half.

Oh, back to Eddie - another way to make your vocals 'jump' is to double them - by recording two takes and using both - worked for the Beatles, it can work for you.

-Scott