MKV, easiest way to hardcode subs?

What is my best option for hardcoding subs? I have a few Bluray rips (in MKV) that have non-english speaking parts. I want the subs to only display in those parts. I know how to get just those subs, but I can't get my HTPC to play ONLY the forced subs. I can only get it to either play them ALL or none.

So, since it's only a couple/few movies, I want to just hardcode those parts.

What's my easiest way to hardcode those and not really change the video quality?

This should probably be in HTPC for more responses, but just create a srt or whatever sub format you want (subtitle workshop is great for this) and mux it into the mkv (MKVtoolnix is a good option for this).

There is no need to "hardcode" subs in, that was an ugly workaround for lack of sub support with early containers. MKV is perfectly setup for subs and you can mux in dozens of subtitle streams and switch to whatever you want in any decent player.

You could try mkvtoolnix. I have never used it for anything but it should work.
http://www.bunkus.org/videotools/mkvtoolnix/