Re: HDMI and ALSA with GTS 450
11025 isn't a valid sample rate for HDMI audio, so your aplay test may not have been valid. Please try a 48000 or 44100Hz sample.
The speaker-test results sound odd. Can you try hw:0,3 as the output device rather than plug:hdmi. That will directly drive the HW rather than layering various plugins on top of it.
Either way, it sounds like the audio driver is having some basic problem communicating with the audio HW. The best people to debug this are probably the alsa-users mailing list, since they have more experience with audio issues.