Duncans right, i had an upscaling player on loan for the weekend,albeit a cheap Tosh, connected with the QED hdmi lead into my Pioneer plasma, expecting it to outshine my Pioneer 575 using component, it didnt! However, i personally could not tell any difference between the two, so for a total outlay of £110, the Tosh held its own with the Pioneers £220, (including cables in both instances)
Maybe the comparison was unfair, especially taking into account the difference in price, but it seems that to get a machine that outdoes a reasonable player using component, you will have to spend a lot more.