i'm not sure how it is on vocals but in general i have heard good things about this summit preamp
http://www.sweetwater.com/store/detail/2BA221/
it's 30bucks more over your budget but i'm sure you'd be able to pull that together if needed
i've also heard good things about the FMR Audio RNP but i'm not sure about on vocals
http://www.humbuckermusic.com/fmraudrnreal.html
that is 2 channels for 475