Vista - Recommended TV card to support a Digital Set top box (Ireland). Vi

I've Vista Ultimate on a HP Media centre PC.
I've an Nvidia 7500 video card and i connect it to a 50" plasma via DVI.
I use the PC mainly for the media centre TV functions. I watch/control my TV
through the PC
The TV card has just blown.

Question:
I have cable tv into a digital set top box and will connect the TV out of
the box to a new TV card. (Im based in Ireland, so only cards that support
UK/Ireland STB's please)
1. Whats the best TV card to support this configuration? (I would like a
twin tuner unit)
2. Any recommendations on whether to replace my video card to get a better
TV picture? (currently my TV picture quite frequently locks up for a min or
two, plus th eimage is a litttle to grainey).
All tips appreciated!!
Thanks