If I understood you correctly, you need to turn the input gain up so high to hear your vocals over the song playing back. Then your problem is not in the actual preamp, it's in your monitoring chain. If you are able to clip the preamp talking, that's way too loud for recording. You're probably getting a plenty hot signal going in, you just need to adjust the ratios of what you're hearing during playback/recording.
The software monitoring program is most likely exactly the issues. I'd read you have everything turned up to zero (you wrote something like that, forgive me for not going back and finding the exact quote) in that program. Well, that program is (I'm assuming here, but pretty sure) basically a software monitoring/routing mixer. That is, it gives you the tools to decide what things go to your speakers, headphones and other outputs on your interface, and in what amounts. So find the channel in there that controls the level of the song playing back from your recording program (probably labeled something like "from DAW") and turn it down. Make sure your input channel's level is at a decent volume, and you ought to be able to hear yourself fine.