Mark,
Dunno about support for your cheap tablet - guess you'll have to Google to see how well it's supported with unofficial ROMs - but I have installed the release version of CM9 on my Galaxy S II.
I had some trouble finding a single guide that worked for me (as there's a a fair few out there, and I found some tools wouldn't work for me e.g. the Heimdall Suite), but by using a mixture of info from the alternatives, I got there eventually. If you're trying to do the flashing using Windows, I would advise that you thoroughly uninstall Samsung Kies before you start, if you've already got it installed. This is particularly true of the Kies USB drivers which need to be uninstalled separately from the main Kies program in Add/Remove Programs. This will stop the drivers conflicting with the modified USB drivers that are used by the flashing tools like Heimdall or Odin.
I'd also direct you to this issue I stumbled across last week:
http://forum.xda-developers.com/showthread.php?t=1756242
It may not apply to you, but you may want to read up on it if you’ve upgraded to stock Samsung ICS 4.0.4 and are then considering rooting or flashing your device with a custom ROM. There’s a bug in an eMMC chip in the Galaxy S II which that latest stock Samsung kernel doesn’t protect you from – if you make the mistake of triggering it, it can brick your device permanently.
If you’re only flashing stock Samsung ROMs, this shouldn’t be an issue. To be absolutely sure it wouldn't cause me a problem, I downgraded to stock 4.0.3 before I rooted and flashed CM9.
HTH,
Peter.
P.S. Also note that the TV out feature of the Galaxy S II is not suppported in Cyanogenmod and probably never will be.