Just so everyone can see this, I'll leave it here.
First off, when your using vocals you need a clean, dry version of the vocal otherwise any mixing or effects you do/add will sound like complete crap. Unfortunately, it is EXTREMELY hard to find vocals especially for a song you want to remix and if you do wind up finding them, consider yourself lucky.
To get around finding a decent vocal, you can always use an a capella someone created., sing your own vocals, or what I recommend, cutting out a part of the vocal you want use with next to nothing going on in the background and re-sample it. This works well for remixes because it gives you the chance to really make your melodiesLots and song structuring skills stand out. Lots of people (myself included) rely too much on vocals to keep the song going. You'll notice most songs with vocals are very boring without.
As far as making the vocal stand out, this all reciprocates to getting a good vocal. You want to make the vocal loud, but you don't want it to overpower the intruments. I would reocmend layering two samples of the vocal on top of each other making sure to slightly offset the vocal. This gives it some prescence and makes it feel like there are a couple people singing rather than just one stereo sound.
Give that a try and let me know how it goes.