I was going to suggest the Truesense Sparse 8050. I think there is another one similar the 16200. QHY has a 16200 6 micron 60% QE built in filter wheel and OAG coming out in a short while. I am sure there will be a OSC version.
The KAI6050 is an APS sized 5.5 micron sensor. Although I am not sure about the performance of the 5.5 micron Kodak chips. The same pixel size is in the KAI29050. If you look at the Cedic images from Chile the ones using an AP175 and Proline 29050 are the weakest images whilst the KAI16070 (full frame 16mp) and the Proline 16803 are the best.
The Starlight Express MX26C is one to look at and the venerable SX 25C has a long history of good images.
http://www.sxccd.com/trius-sx26c
Or the QHY version of the same sensor:
http://qhyccd.com/QHY10.html
The Trius has the 3 usb ports and you are already setup with all the drivers etc. The 3 usb ports are handy. I don't know about QHY versus Starlight Express for quality and reliability. But QHY is probably cheaper.
Greg.