No problemo that you asked, better safe than sorry
So, you want CM9? You can flash one of the defy+ builds by Epsylon, Quarx or FuZZ; links:
http://defy.wdscript.fr/defyplus-cm9/
http://quarx2k.ru/cm9-nightly-defy+/
http://fitsnugly.euroskank.com/skankwich/?id=jordanplus
The FuZZ one seems to be best in terms of features and speed, but the other two maybe a bit better on the battery life side.
These are the builds you need and you shouldn't flash defy builds as they are meant for Froyo (froyo kernel, that is). You asked about kernels and I guess you figured already - you have a Gingerbread kernel on your phone. (You can't flash any other kernel as those flashable kernels are meant for standard DEFYs that have a lower bl version than DEFY+. If you flash one of those on a DEFY+ you will end up being stuck in bootloader and having to flash a full sbf. A pain in the ass that you don't want
)
So, when you see defy or defy+ builds, think this way:
defy = Froyo
defy+ = Gingerbread
And now, the steps you should take to install one of those CM9 builds:
1. Install 2nd init (if you haven't already?)
2. Get into custom recovery (you should copy the ROM zip file you downloaded and a gapps.zip (
link) on the root of your sd card )
3. wipe data
4. wipe cache
5. advanced \ wipe dalvik cache
6. install zip from sd card - install ROM
7. install zip from sd card - install gapps
8. wipe cache
9. wipe dalvik cache
(steps 8 & 9 aren't necessary)
10. Reboot!
11. Enjoy