The xenyx line is meant to be a knock off of the Mackie Onyx line - and they've done a pretty good job at it. While I haven't compared them side to side, as long as you aren't overdriving the channels the Behringer seems to sound quite good. No, it's no A&H or boutique product, but for an entry level workhorse, it's really not all that bad...
BTW, I should know, I have a Mackie Onyx 1620.... complete with a firewire card.... (which will be up for sale soon - time to downsize!)
Of course... I still have a M-Audio NRV-10, Soundcraft Compact 10, Behringer VMX-1000, a couple Numark DJ mixers, and probably a couple others lying around... Time to clean out the closets!