It's worth bearing in mind that upgrading to Tiger will require you to upgrade your memory by 512Mb.

Tiger has it's own set of issues, but so far I have not observed any of the tearing and stuttering issues associated with the later Mac OS 10.3.x builds.

One thing to look at in Tiger is Quartz Composer. Catalyst (run under Tiger) will playback Quartz Composer compositions. RSS feeds/Midi/Audio stuff is not supported.

I have recently acquired a 2.3Ghz Dual Core PCIe Mac, and the performance on the nVidia 6600 is looking okay. Still waiting forward to the dual core 2.5Ghz and SCSI controller card.

Hugh