Composite to VGA... I use a "Viewsonic VB50hrtv" box myself. (Yes, I use it with my DSM-510) It has 15-pin VGA output, a TV tuner as well as composite input, and a VGA input so you can "pass-through" your computer signal (to monitors with only 1 input). also has a remote.
I found it through local craigslist ads, for $25 used.
I've also tried the "RTV VEG Lite" with similar features except no TV Tuner, and I think no remote. Personally I like the stability and features of the Viewsonic better, but if you find either one for a good price I'd say go for it.
...I saw similar boxes on Amazon called "V2VPRO" and "Geniatech HD Gamebox" but I haven't tested one.
Good Luck!