mkv encoder / converter advice

[greendesert]

1) Is there any software which will convert all (mainly xvid, divx, wmv, mov and flv) files to mkv ?

2) And where I could define the output size ? e.g. in auto gk we can define the output size, something like that ?

I am planning to buy WD HD media player as I have loads of huge video files which are unmanageable, so I want to convert
them to mkv ( I believe the same video quality at lower file sizes).

[Baldrick]

1,2. Handbrake. Set the output size under the video tab.