To be a little more specific....
The API is a rack mountable modular mixer solution, primarily designed for summing and tracking. First you buy a master section, then you buy either preamp strips for it or line input strips. This means you can buy as little or as much as you want and get a killer setup in the process.
Neve now makes a 16 channel summing mixer that if I remember right, may even have some preamp and/or EQ options built in as well. I have not personally seen or used the new Neve one as it is brand new. I think it is shipping now though.
Trident (the John Oram trident) makes a small rack mountable mixer that does have preamps and EQ's, and you can also add a fader extension to it if you do not want to use pots for channel volumes etc...
Midas makes a mixer that is a standard 4 buss 6 aux mixer that fits in a rack mount as well. It is a Venice, but I am not sure which model since I have always bought the full size Venice 320 which has 24 mono inouts and 4 stereo inputs and is NOT rack mountable.
Amek I believe makes a rack mountable mixer, but may not be in current production. I may be wrong about this one though, they may not have a rack mountable mixer.
Manley also makes a 16 channel tube mixer (rack mountable). You can buy this one with line inputs only, or with preamps also. The price varies depending on which one you buy, and the I/O count may only be 8 channels if you buy the one with the preamps. It has been a long time since I have touched one of those, so I do not remember completely.
Chandler also makes a mixer called the TG rack mixer. You can customize the Chandler with as many or as few channels as you want, and select individually between line in channels (mostly for summing) or full on TG channels (tracking/mixing). The advantage of the Chandler is that you can also choose to add the TG compressor to the master section which is an awesome otpion.
Of all of these, the Midas and the Neve summing box and the Trident would be the cheapest. The Manley is pretty spendy, and the base packages for the Chandler and the API are also pretty expensive. The advantages of the API and the Chandler is that you get VERY high studio quality pieces that are fully modular so you can start small and add as you see fit. The Speck is also a good option, but if you start adding preamps and EQ's, than it is not nearly as affordable as it may initially seem. Personally, the others are of higher quality, but the Midas and the Trident would probably be pretty close as far as raw sound quality goes, not to mention they would take up less space if you decide to end up with 16 full channels.
That should arm with with some information to get you a little further along in your search. There are certainyl other good offerings form other companies (maybe Daking, Shadow Hills etc...) but those are the ones that popped into my head first. Good Luck
