I do not think there's any support for the x10 from CM for the v9 release.
For reference:
- Xperia Arc => anzu
- Xperia Neo => hallon
- Xperia Pro => iyokan
- Xperia Mini Pro => mango
- Xperia Ray => urushi
- Xperia Mini => smultron
- Xperia Arc S => ayame
- Xperia Neo V => haida
- Xperia Active => satsuma
- Live with Walkman => coconut
- Xperia Neo L => phoenix
Edit:
CyanogenMod is a ROM that targets a lot of handsets. A souped up/bloated version of the Stock Vanilla AOSP Android (the ones found on the Nexus series handsets)
The FreeXperia project was founded by jerpelea who (unofficially works for Sony, gets freebies and contributes to porting CM for that handset etc). Also, FreeXperia project is officially merged into the CyanogenMod tree. Not all legacy devices are supported using the CM ROM, especially for the newer v9 and v10 (ICS and JB respectively.
If visiting this Get CM you will actually find that CM is not supporting the legacy devices!
Have not tried FreeXperia, but have heard it is not 100% stable, as some things are broken on it (If anyone wants to correct me, feel free to say so in the comments) :)