As for video cards, I would recommend pretty much anything from nVidia
. Their current proprietary driver support is much better than ATI, although that may change in the future with ATi's commitment to developing OpenSource drivers.. but hey, we're talking about now, not what may or may not happen in the future. I have a nvidia 6800 card in my PC, only because I'm strapped with an AGP port.. if I had PCI Express I would have a faster card in there for gaming.
Desktop effects ? Look at Compiz
You WILL need a semi decent card to get this working, but it will give the the fancy rotating cube, wobbly windows, and those effects you are interested in ..
Super Tux.. can't say I've played that one. If you have any or the Quake, Doom, neverwinter nights or UT games for widows you can install them on Linux.
Loki provides installers for some other older windows games.. http://www.lokigames.com/support/
Savage is native Linux and now free to download and play. Savage 2 is still in pre-beta but is around $35.00 http://www.s2games.com/savage/
bzflag Battlzone tank game with power up flags. good for a quick hit and run gaming session. http://www.bzflag.org
There should be other games in your Distros repository.. or you can checkout some of the Linux gaming sites.
You can also subscribe to Cedega so you can play your windows games on Linux (free versions of Wine, winex, or Cedega CVS can also be used ) http://www.cedega.com/
Ok so your gaming options are hardly limited..
HDTV hookup .. I dunno on that one. I'm too cheap to invest that much into a TV right now...
Outgrow Suse. Well Are you happy with it? if so stick with it, although it never hurts to look at other disros. They can all offer pretty much the same thing in the end, but the tools to get there will be different. If you want more hands on with configuration files and the like, then look at Debian, Slackware, Gentoo. You can install the free vmware server
on your current Linux box and install all of these distros into virtual machines to try them out.. Hey you DID ask for something else to do on your machine other than LAMP
glad you are enjoying your Linux experience
I forgot the link to a Linux hardware review site.. Motherboards, Graphics cards etc.. http://www.phoronix.com/scan.php?page=home
and of course LQ's HCL has info as well.. http://www.linuxquestions.org/hcl/