"ou don't need to change your USB interface with Vista,
but it may not pass 24/96, so you couldn't use Vista's upsampler."
One should NOT just accept that 24/96 upsampling will always sound better. Quite honestly, in most of the lower quality DAC implementations this is quite the opposite.
Simply adding random bits doesn't always contribute to the transfer of information from the analog input signal to the digital out, thus carrying no sonic content. Because ultimately the criteria for quality of the converter bits depends wholly on the converter linearity, and with a linear circuit this will insure proper transfer from input to output. Thus retaining the sonic detail and benefits of up converted bits.
In the end the technical difficulty of retaining the linearity grows with each additional bit added, particularly when dealing with everyday engineering formulas and standards. In production-based implementations like the aforementioned equipment, with commodity based DAC chips, this is often the case, with a sonic result that does not sound anything close to music.