They all look good to me. Yes, the background noise can distract but I still think more data stacked would clear up the noise. Make sure you dither between frames though. This will help you put the noise pattern in a offset from frame to frame. That way it will mean or sigma out better.
http://www.hiddenloft.com/notes/dithering.htm
THis example (from 2003) uses dithering in CCDSoft, but Maxim and many other control programs can dither now.
Tom