The Presonus Eureka OWNS, slinger. It's awesome. Matt and I used it for the latest track we recorded (clip posted in the eggy forum).
It was reccomended to me very highly by a friend who owns and runs a well known studio here in NJ, called Portrait Recording Studios.
I scored mine on eBay, it was a B-stock/open box special for like $379 from an ebay dealer, HollywoodProAudio.com. When I got it, it was flawless, brand spankin' new, not a scratch on it.
I can now fully attest to the statement people make, when they say "if you don't like a SM57, try it thru a better preamp, because it will sound like a totally different mic." Couldn't be any more true. We used a single SM57 thru the Eureka, into Protools, and got the BEST guitar tones to date. I'm sure it has something to do with the fact that the preamp input is transformer coupled - whatever the hell that means.
Not to mention a really well designed, great sounding parametric EQ with overlapping frequency ranges, and an awesome, clear, punchy compressor built in. And a host of other great features. The fact that you don't have to have a low shelf, parametric mid, and hi shelf is awesome. You can have low, low mid, mid. Or mid, mid high, hi. Or no EQ at all and hit bypass. Great EQ feature.
From what I've read, the bottom line in preamps is:
If it's TUBE: Don't even bother if it's not running at high plate voltage, or else all you're gonna get is fuzzy distortion. If it's running at starved-plate voltage, it's not gonna be the *REAL* tube gain that you want. The warm, fat, clear kind. it's gonna be tube fuzz.
(I can attest to this. I own a ART Tube Pac - $130 preamp/comp. while it sounded decent to me, once I got the Eureka, I realized that it was just a glorified fuzz box).
If it's SS: Dont' even bother if the preamp is not transformer-coupled (meaning, make sure it's not driven by some little IC chip).
If you want ONE preamp to do it all, I'd go SS. Tube preamps can be VERY very colored, and you may or may not want that color in ALL your tones. The eureka has a saturate feature, which works well to warm things up, a la tubey goodness simulation.