NEW YORK (CNNMoney.com) - What's the single most-important thing on Super Bowl night?

Here's a clue: It's not the food, or the parties or even the teams facing each other. Rather, it's all about the "image." So once again, the real Super Bowl winner is -- the TV.

Photo Gallery See more photos

Since Super Bowl is the most-watched television event of the year, it's regularly a top driver of new television purchases, according to the Consumer Electronics Association (CEA).

"TV sales tend to be related to major television events like the World Series, Super Bowl or the start of the Fall program line-up. Super Bowl gives a huge boost to TV sales," said Megan Pollock, spokeswoman with the CEA.

Keeping with tradition, millions of Americans will upgrade their sets in time for the big game. The National Retail Federation estimates that consumers will buy 1.7 million new televisions ahead of the event this year, up from 1.4 million for the same period last year.

ABC is also broadcasting the game in high-definition (HD). Five days later, NBC will begin broadcasting the winter Olympics in high-definition.

Both events should act as a strong catalyst for sports enthusiasts to upgrade not just to a digital TV (DTV) but a high-definition digital television, Pollock said.

"We did a survey last month in which we asked people what was their favorite event to watch in high-definition and 79 percent said it was Super Bowl," she said. The same survey showed 54 percent cited the Olympics as their second-favorite sporting events to view in high-definition.

As prices for digital TVs continue to scale down -- current prices vary from as low as $500 to more than $3,000 -- more consumers are migrating to better technology.

The CEA estimates a total of 12.3 million DTV units were sold in 2005 with sales reaching $17.5 billion. Electronics seller Best Buy (Research) logged triple-digit growth in flat-panel TV sales just in December. The group projects that another 18.7 million units will be this year, totaling $23.3 billion.

If you're one of the millions making the switch to a digital set before the opening kickoff, here's what you need to know:

-- Digital and high-definition is not the same thing. Not all DTVs are high-definition TVs. DTVs come in three formats defined by image quality: Standard, enhanced and high-definition.

"Our research shows that 85 of people who buy digital sets choose high-definition TVs because the image quality is much sharper," Pollock said.

-- Does your cable service operator provide HD programming? DTV (including HDTV) is available over-the-air using a standard antenna or via digital cable or satellite. But no matter how you receive the TV signal, consumers will need DTV equipment to watch digital programming.

Some DTVs are already "digital cable ready." These can be used to receive digital cable TV (including HD over cable) without a separate set-top box. Otherwise, a CableCARD is needed to watch certain cable programming. But these televisions don't work directly with satellite and will require a set-top converter box.

For those consumers who already have a DTV that isn't high-definition, they can buy a standalone HDTV "tuner" or an HD "antenna to access the HD programming.

Finally, if you're just not yet ready to upgrade to digital, you'll still be able to watch this year's HD Super Bowl without a digital set, "but the picture won't be as enhanced," said Pollock.

-- A bigger screen size isn't always better. Screen sizes vary according to the DTV format. Liquid Crystal Display (LCD) screen are typically less than 30 inches; plasma flatscreen TVs are between 34 to 61 inches; bigger flatscreen, rear-projection screen range from 40 inches to over 80 inches.

Experts say screen size is typically a matter of individual taste but it also depends on the size and shape of the room and your budget.

Kevin Winneroski, head of flat panel sales at Best Buy, said many people are buying bigger sets only because the prices have come down. For instance, prices for a 32-inch are down to $1,599 this year, almost half from where they were in 2004.

So while the 32-inch screen remains the most popular size, customers are quickly moving to 42-inch screens," he said.

"If you sit close to the TV, you don't need to buy a very large screen," Pollock said. "The general rule of thumb is take the diagonal of the screen in inches and multiply it by 3. That's the ideal space to keep between the set and yourself. "

And a projection TV might be a better idea if you like watching the games in a dark room, she added.

--What brands should you buy? Again, it's a matter of personal preference.

The good news for consumers is that no one manufacturer yet has a monopoly in DTVs. That means prices will remain very competitive as established brands compete with relatively unknown brands for shelf space.

"Different brands have different functions that are unique to them. The mainstream brands like Sony, Panasonic and Pioneer cost a little bit more than say Best Buy's own Insignia brand but the functionality is just as good," said Jim Hart, a division manager with Best Buy.

His final tip to consumers is to look for some good package deals. "This is the best time to get a new TV. Besides the five to 10 percent discounts, people can get a free surround sound system thrown in and better financing deals too," he said.

------------

For more about Super Bowl XL's extra-large ad sales, click here.

For a recap of last year's Super Bowl ads, click here.