Converting my Blue-Ray collection to small MKVs

I have purchased about 100 blue-ray movies over the past few years. However instead of having to use the physical media, I want to convert the mvoies to MKV files and keep them on my NAS and stream them from there, which will be easier to handle. After trying out a combination of AnyDVD HD and MakeMKV utilities, I am now able to convert my Discs directly to MKV files. However the problem is that these MKV files are the same size as the Original Movie = anywhere from 25-40 GB each. I need a solution that will down-convert the bitrate so that the end result MKV is no bigger than 10 GB. Otherwise my streaming media player will have problems with it. More specifically, I need a written step-by-step guide, that will meet the above needs.