Mixer Question - Doubling of tracks

[citi]

Okay here's the deal,

Previously I ran my synths into the stereo ports on my behringer but I was getting some low level hum that I didn't like so I moved them to the mono ins. The hum went away.

I have my keyboard and my synth plugged into 4 channels on the behringer mixer. Basically acting as a left and right for each synth and module. The last track I did sounded really hot but in a good way and then I realized why. I was getting the stereo the left and right channel mixed into the output. (maybe this is obvious to some) Basically the track is being doubled.

Anyway, my question is: Will this hurt the overall quality of my sounds, like the kick or snare being unaturally too full (this might seem dumb, but I just don't know) Should I stick to single recording. I know the rule use your ears, but a little technical no how never hurt anyone. Open to all opinions.