I had to use mode 720x576Over. It's the only one that works for PAL with the VT1625M chip. Also, I'm finding that I'm getting smoother playback with ffmpeg decoding and XVideo blitting, rather than XVMC.
As with the other board, good quality picture requires turning off as muh processing as possible, so no scaling, and TVDeflicker disabled.
The only down side is that I've lost SPDIF. I'm hoping I can find a fix for that.
Pablo: Minimyth docs say MM_X_TV_OUTPUT='YCbCr' is untested. I can confirm it works.
I have no idea why the extra audio buffering setting affects the smoothness of video. I noticed the lack of smoothness when I very first used the setting, but then convinced myself I must be imagining it. My son, home from Uni for the weekend, noticed the lack of smoothness straight away, and confirmed that turning off extra audio buffering cured it. The problem was noticable only with Standard xvmc: using VIA xvmc seems to allow use of extra audio buffering, without loss of smoothness.
Lately I've build a larger fanned system based around a motherboard with a built in X1250. That, using the radeon driver can produce 720x576i from VGA, which I run into a VGA to Scart circuit. This, at last, gives me picture quality as good as, or maybe slightly better than, my old DVRs.