The volume control only effects the 1/4" jack on the front, not the volume that comes out the rear connectors. :-)
As for the games, pass. I got that information from a games flyer that came with the CDTV.
Apart from games that dont kickstarts above 1.3 the only real difference is the A570 doesnt have the memory card slot.. so I would think "most" games would still work.
While I work at getting a new hosting company, you could always use the archived version from the wayback machine at:
http://web.archive.org/web/20050308152017/http://www.cdtv.org.uk/index.html