I guess it does not really matter. A TV card with an encoder chip takes away the load from your CPU, that is then available for the streaming. However that depends on how much power you have; if your PC is state of the art it might not be a problem.
Also consider that streaming MPEG2 video (what hardware encoders create for you) over a network is only feasible on very fast LANs, not over Wifi or internet. In that respect you'll probably want a raw video stream anyway, and use transcode in Videolan to create an MPEG4 or DivX stream. My point is in that case it does not really matter whether you have a TV card with or without hardware encoding.
Having said that I recently bought a Hauppauge WinTV PVR-150, which is redesign of the PVR-250 and supposed to replace it. I'm very happy with it. However I'm not sure it is available in all countries, or wherever you come from.
A site that is a good startingpoint for choosing a TV card is
http://www.tv-cards.com, but there are many more. Google on "tv card" and "htpc".