Hmmm... When you said
HD-PVR, I automatically assumed the
Hauppauge HD-PVR, which is what some of the members here use to capture HD broadcasts. Here's the product I'm referring to:
http://www.newegg.com/Product/Product.aspx?Item=N82E16815116030I think I may have thrown myself into a fairly complicated situation.

But I'll try to lead you the right way the best I can.
I'll try to make this post as short as possible so I'll list each of my concerns/suggestions in order.
1. That Shaw cable box should be a good start to get HDTV reception.
2. Those two tuners you listed will tune over-the-air HD channels (local channels mostly), but if recording HD
cable channels is what you're looking to do (and I'm sure that's what you'd want to do), then these tuners aren't what you want for that particular purpose (otherwise you'd be stuck with dumbed down analog quality video for those channels, but that's another topic).
3. There are a few methods to capture HD cable channels from a cable box to your Mac (or a PC for that matter). One would be to use the firewire method but the cable box you chose does not seem to have a firewire port so we'll exclude this method (I'm not sure if this method can even be done on a Mac anyway). Another method could be to capture the shows through the HDMI port using devices like the ones that
Blackmagic Designs and a few other companies make, but I should say that this is a method unfamiliar to me. A third method would be to exploit the "analog hole" with devices like the aforementioned Hauppauge HD-PVR or the
AverMedia USB HD-DVR, which capture HD shows through component outputs on the back of your cable box (probably the most practical method).
I need to mention that I'm neither Canadian, nor do I use a Mac. Heck, I don't even use any of the methods I mentioned above to record HD cable channels (I use an ATI DCT on Windows 7 for HD cable channels, and another tuner for OTA channels). But hopefully this is informative enough to get you started.