MAX, to be meaningful, the RMAA test has to be done with a cable connecting the soundcard output to the input (rear out has best quality on the Live). I don't remember the names the KX drivers give to the cards ins and outs, but make sure you really have the ones the cable is connecting in the test.
Be careful that you haven't tested with the loop back in the card (a What U Hear record), as this is bypassing the cards analog converters. When you run RMAA you should get a short setup thing where you have to match the output to input gains.
I have seen claims of excellent performance from really cheap consumer soundcards and it turned out they were set up wrong!
The numbers RMAA produces are not the whole story - look at the graphs to see what really happened.
If you have the latest RMAA (5.?), you get two distortion figures. These are a good pointer to any side effects of sample-rate conversion. THD and IMD, IMD especially. The distortion represents frequencies that should not be there.
Maybe I was wrong - this may open us up for more debate than there was in the first place! Still, it's fun. If Toki987 is also doing some tests, then we can get some much needed "control" on this thing
Re Dithering. If your files are going to be professionally mastered then yes, you should definately leave it for them to do. But if you want to make your own CD, then it will be better if you add dither yourself when downsampling to a 16/44.1 .wav.