ffdshow
does support srt and is able to make use of vobsub itself.
I wouldn't recommend codec packs and especially nimo , which is known to cause problems for a long time,
at all.
If you install ffdshow, you really don't need any other codec installed for decoding!!
And as it is totally open source it's free.
The current version (a cvs snapshot), which is not an official binary release at sourceforge, also plays AVC/mp4 fine.
Though officially in alpha stage it runs stable (version 20050122).
Get it
here. No use for codec packs anymore, it's really worth.
(This is no advertising, I mainly use it because it is ATM the only reliable Direct Show solution for decoding AVC streams WITH b-frames)