So we have another MythTV user! Once you get used to it, you won't want to go back. I very rarely watch "live" TV anymore. I record and watch later which lets me skip the commercials.

As for cards it's very dependent on where you live and what channels you have.

The PVRx50 cards sound fairly good and take a lot of the load off the CPU. The driver support isn't all the way there it would seem. If you want to pipe the output of your cable TV in, this is probably what I'd use.

Personally I didn't have much luck with normal "software" encoders receiving analogue TV. I found the insides of a PC simply had too much interference for the tuner to work well. Digital TV (DVB in Australia) gets around that problem

Is Canada the same as the US i.e. ATSC for digital TV? There are special ATSC cards which I think work pretty well from what I've read.

In my setup I don't have cable or anything like that. I have two Hauppauge Nova-T DVB cards and they work fine. I use a Geforce4 MX440 as the output via S-Video and it's pretty good. Running an XP2400 CPU is probably a bit overkill. CPU runs at about 25% when playing back. More CPU is good for transcoding if you are trying to save space though.