Well, that's a tall order. Here's a couple things to maybe keep in mind.
Tube mic pres, like the kind mentioned above, are actually hybrids--solid state preamps that feed the signal thru a tube to get that slight distortion. And unlike expensive, real tube mic pres, they are not silent and they will add some noise. Maybe not audible on one track, but taken altogether...
Which brings me to another point: if you truly need eight channels going all at once, and you're set on getting these pres, consider going with a variety of models to increase your palette. If you find you're really crazy about a certain preamp, you can always return another for that model. You can also have one moderately good one for important stuff like vocals with a couple "cheapies" on the side.
Finally, keep in mind that as preamps go up in price, they make less noise and are usually less "colored," more transparent, and the fact that they are tube or not becomes less important and more a matter of taste. Have fun--wish I was shopping for some too!
