I guess first off - how many RG6 lines do I need for a DirecTV HD box?
That will depend on which HD box you purchase. If you purchase a HD box without TIVO capability or without 2 tuners, you will only need a RG6 line. If you purchase the DirecTV HD box with TIVO, you will need 2 RG6 lines (because there are 2 separate tuners in that box. I have that box and I am very pleased with it. I also have a regular HD box that works well for my other TV. This will all depend on whether you want TIVO capability and whether you are willing to pay the extra cost of the HD TIVO unit.
What approaches will work with CSR to get discounted equipment?
I would suggest that you contact customer retention directly (800) 600-8977 and suggest to them that you can get HD cheaper with cable and are thinking of switching to cable. Most of the time, the CSR will offer to give you some discounts on purchases of equipment and programming. If you don't like the offer given you, you can play CSR roulette and call again and speak to a different CSR.
With respect to superfan, that is necessary to purchase in addition to Sunday Ticket if you want to see the games in HD. There are several extensive threads on this issue in the HD Programming Forum here on AVS. There have been very recent announcements that the charge for Superfan has just been reduced from $99 to $49 for existing Sunday Ticket Customers. Others have been able to obtain discounts on Superfan by talking to a CSR in customer retention.
I can't help you much with picking on OTA antenna as that is very highly dependant on the exact location of your house. You could also consider getting a basic cable package that might give you local HD channels if that is available in your area. If you live outside the local viewing area of the network stations, you can get HD network channels from NY and CA through DirecTV. However, I assume you are probably too close to the local network stations. Some people have been able to qualify for these distant network signals from DirecTV by "moving" to another location outside the local stations areas.
HDLite refers to the fact that DirecTV is not broadcasting the HD stations at their full HD resolution. Whether the resolution they are broadcasting at can really be called HD is the subject of some dispute. The signals still look very good, but if you have a very large screen or are very fussy about the quality of the signal, you may notice the difference.
MPEG4 is the new method that DirecTV will be using to broadcase HD signals in the future. Many people believe that DirecTV will replace the customer's equipment with new equipment when necessary for little or no charge, but there is no guarantee of this.
With respect to DVI issues, you may want to check the HD Hardware forum here on AVS.
I hope this helps to answer your questions on a basic level. There is a lot that could be added for each of your questions and I am sure others will add their comments.