The preamps on nearly any budget board will be an area of compromise. You can pay all outdoors for external preamps; the going rate for our market is around a bundred bucks a channel. The next price point (Grace Audio) is about $500 / channel, and the one after that (Avalon) is about $1,000 - per channel. Neve preamps - pulled from the 1970s decks - are available rebuilt at about $1400 a channel. Crazy. Kind of like looking at boats; as soon as you know anything about them, you know you can't afford it.
How about just going for the unit and keeping in mind that the M- Audio preamps can be had about $35.00 a channel? Hard to beat that, and if you want to upgrade to preamps later, you can on a safe budget. I just might do the same...