Leadfoot
I would still like to pick up an old Tascam US-2400. 25 motorized faders, and you can usually find one on eBay in great shape for about $600. They appear to work well with Sonar. Not sure about CbB.

There is a US-2400 for sale almost right next door to me for under 100$. Only missing a fader cap (and I've got that on my FW1884).
Can't really afford it now, and not sure it comes with some of the functions I've grown accustomed to.
Would be nais with 24 faders, though
All the best.

I used a couple of behringer BCF2000's for a while, which were great as controllers, but as they don't have a display for the track names I found myself constantly looking back up at the monitor to see what track was what.
 
In the end it was actually quicker to just use the mouse (or in my case trackball).
 
As the US-2400 doesn't have a display, I'd bear this in mind.
 
It's probably fine if you're used to using the same tracks for the same things for every song (e.g. you might when recording bus automation in your final mixdown), but for general track mixing, you might find 24 un-named tracks bewildering... but then again, maybe not, and it IS one of the coolest looking control surfaces out there.
 
I've since moved to a Mackie MCU + XT + C4 which is far better due to having the display.
 

The MCU Pro is very solid.  You really need the Cakewalk overlay template, so look for that if buying used. 

msmcleod

 
As the US-2400 doesn't have a display, I'd bear this in mind.
 

I suppose this was for me, so I only quoted this
My FW 1884 doesn't have a display either, so I'm used to it 
I often use Console 1 to highlight tracks and scroll/tab banks of faders until I find it in the 1884. Not ideal, but much better than not having it at all
All the best.