read read read and research
You could start by reading the review of the Coolsat 8000HD on the equipment review section here. HD receivers are still very young in fta, sev manufacturers are now coming out with hd boxes, Read their websites -coolsat, pansat, fortec, viewsat and several others are now selling, or about to sell new versions of hd-receivers. They are still mostly too new to have good info about yet, but at least the specs are available to read. There are many variables, and virtually none will do ALL hd signals.
And then, many users opt for fta-cards that go into their computers, for the
hd signals. I think you need a fairly fast computer/graphics card for those to operate well.