I would pay the 60$ for the house call and get a quote for the repair. With the cost of DLP plasma and LCD dropping I would make a decision after the quote. If you tell the repair company that your leaning toward a new television if it costs to much you will most likely get a better deal
I think the difference between the 2 cables is more distinct depending on the type of tv. I see a huge difference on my television between the 2 and I have a JVC HD-ILA but most of the installs I do on plasma or LCD the difference isnt so much. Just remember to use good cables