What I recommend is to get both. I'd get a blind scan reciever and a Twinhan card. This way you'll have the best of both worlds. You'll have the blind scan capability of the reciever along with the ability to do things like HD and 4:2:2 with the twinhan card. Recievers that have those capabilities (HD and 4:2:2) cost much more than the cost of a twinhan card and a good blind search reciever combined and If I undertand correctly these recievers also do not support blind scan or at least the most common and cheapest ones don't. So, by combining the 2 you'll not only get something that's much cheaper but in fact has greater capability.
The twinhan cards are great because they are cheap, support high symbol rates, and DO NOT have a hardware decoder onboard. Because they don't have a hardware decoder onboard and the hardware decoding is done in software, it makes them much more flexible. That way if a new video compression technology comes along (like say MPEG4) in theory it's simply a matter of someone writing software to support it. In contrast let's compare them to a hadrware decoder card like the Nexus. With the Nexus card you have an onboard MPEG2 decoder. Now that may sound good initially but let's look at what that decoder supports. If you do you'll find it only supports 4:2:0 at Standard definition only. Seeing as how just about any PC made in recent years can do this with very little CPU usage, it kinda makes the whole thing moot and useless. Of course at the time the card was designed the hardware decoder was probably state of the art, but by todays standards it's pretty much useless and a waste of silicon. So as you can see the Twinhan approach of software decoding was a much smarter approach in the long run. Some may agrue what's wrong with having the onboard decoder even though it's not usefull. Well, the answer to this is it increases the cost of the card, increases the power consumption, and increases heat output all while adding no real advantage to the functionality of the card in any modern PC.
As for recievers, I have a Pansat 2500a and I'm pleased with it. My understanding is the 2700a is pretty much the same. One nice feature with the pansats is they have digital audio outputs that can pass AC3 audio.