pinnacle studio ultimate is a really good place to step up from WMM into something thats a bit more professional.It handles my AVCHD from smy Sony perfectly, and outputs in decent quality formats.
Its about £100 for the ultimate version, and includes a good array of effects. One of the good features I like about it is the magic bullet looks which can really transform the feel of the movies. It also has the stabilisation which is OK, but personally I've never really needed it.
Maybe a little weak on the music side of things, but I use audacity to trim music clips together and do sound effects etc ( remove voice ) , then lay that into the timeline. That being said, adjusting the volume for bits of the audio is dead simple.
Give it a look, there is a 15 day trial you can download from the US version of the site if you go looking for it.
A couple of vids I've done with it recently … the colour styles are direct from the magic bullet looks effect plugin.
Craufaudland MTB
Irvine MTB
I'm really pleased with it so far.