im in the exact same position as you.
Ive heard that a cheap mixer will give you a cheap mic preamp, but you can get a really good mic preamp for cheaper. Its just not as versatile as a mixer. But im going with a mic preamp, you'll see in my post below im asking about the art preamp, because ive heard its reallly good, and its cheap.
I have the ART dual mic pre -- it's a good piece of gear for the money. I've used it for several years and you can not only run vocals through it but, as well, bass, keys, etc.
But, I must mention, now that I use the Yam 2816, I use its mic pres and they are good; but, that doesn't mean that I would not use the ART into the Yam if I thought I needed it.
There are many mic pres out there and many prices. You can't miss with the ART but if you spend more, BE SURE to hear before you buy.