The only affordable mixers with really good preamps, at least to my ears, are the later VLZ-Pro Mackie's (1202, 1402, etc.). Vastly better than anything by Behringer, Yamaha, etc.
The improvement over the original ("non-Pro") VLZ's is HUGE.
Aside from having less noise and sweeter highs, they also have a wonderfully solid bass response. Until these came along, I wouldn't plug my 5-string bass direct into any mixer. All of a sudden, my fancy bass preamp is obsolete...
These preamps are also much better than the internal mic pre's in the digital multitrackers I've tried.
Steve Rolfe.