I have been planning to get a Mackie ProFX12 when I can find one in stock.  It looks like just what I need.
Learning about Mackies problems with chinese production from this Forum, and the fact that it 
has been hard to find available, has caused me to re-think my choice.  So I have been looking at other non-powered USB Mixers.
It looks to me like the Allen & Heath ZED-14 is a better choice than the ProFX12.  Of course the cost is greater. 
 http://www.allen-heath.com/zed/zed-14.asp
 
http://www.allen-heath.com/zed/zed-14.asp
Two features that I like are; 1. You can route the USB input into a stereo return, allowing much more control of the music on the mixer( the ProFX appears only to have a USB gain) 2. Swept mid-range control.   It doesn't have built in FX or EQ, but I recently bought a Lexicon MX200 and plan on a DBX Driverack down the road, so thats OK with me 
 
 
I Would like to hear what others think of the ZED-14 and how it might compare with the ProFX12, or maybe other sugestions for a 
USB unpowered Mixer.