Upscaling options certainly exist. You can buy an external upscaling unit, though be aware that these usually start at around £500. I chap I used to work with blew close on £2k on his.
Another option is one of the newer AV amps, some of which have multiple video inputs and can upscale and output via a single HDMI. An example of this is the Onkyo 875. Comments on the net are that it's rather good at it, though it does cost a cool £1k. Having said that, it's also supposedly rather good at surround sound, so in terms of functionality/£ it's far from bad.
Having said all of that, I really couldn't tell you whether that would result in SD looking good on certain TVs, particularly LCD units. My personal preference would be a decent plasma.