Well, I won't tell you what to do, but I personally wouldn't buy a Behringer pre amp. I would buy a Behringer direct box, patch bay, headphone amp, or something that I know won't really affect the quality of my recording, but not a compressor, mixer, pre amp, or anything else that could cheapen my sound. A direct box is straight forward, so is a patch bay, but a cheap pre amp can box in your sound and ruin your recordings. I am using an inexpensive $300 mackie, but when I do spend money on a pre amp I will most likely be getting the DMP3. Its only $175.00 I think , and i only hear good things about it.
EDIT: I see you are looking for an 8 preamp unit. I wouldn't know where to point you on that one. Anything you buy with 8 preamps thats worth using is going to pretty expensive. I guess you should mention how much money you are willing to sepnd, because with a tighter budget you could get a decent analog mixer with good pre's. But if you have plenty of money then there are tons of options.
Couldn't you get a a decent mixer with lots of pre's for the everything but vocals, and then bhuy a dedicated pre just for vocals. For instance if you bought a yamaha MG16 you would get the 8 channels of decent pre's, and then you could buy a dmp3 for vocals or something similarly priced.