(MONEY Magazine) – Whatever the Atkins diet has done for the American waistline, it has indisputably loosened the American attitude toward red meat. Eating steak is morally and nutritionally correct once again. It's a diet food.

But really good steak remains hard to find. Supermarkets don't carry it. Old-fashioned butcher shops might, but good luck finding one. It may sound like heresy to shoppers who like to see their food before they buy it, but if you want to serve the best meat, your wisest bet may be to get it by mail. At $35 to $45 a pound, it won't be cheap. But then, nothing first-rate ever is.

What qualifies as first-rate beef? At a minimum, it's rated "prime" by U.S. Department of Agriculture inspectors, based on the amount of fat marbling. The rivulets of fat running through the meat—the more the better—create steak's juicy flavor. Just 2% to 3% of American beef makes the grade, however, and much of that goes to steak houses. Moreover, only a small subset of that topnotch beef is dry-aged, a time-consuming process that tenderizes the meat while concentrating its flavor.

Supermarket meat is usually graded "choice" or "select"—the two levels below prime. Store-bought beef is rarely aged at all, which explains why so much of it tastes like cardboard. Even in a gourmet shop or at a high-end butcher, prime cuts are often wet-aged—a shortcut in which the meat is cryo-sealed in its own juices—rather than dry-aged. This helps with tenderness but does nothing for flavor and is more a marketing gimmick than a quality enhancer.

A handful of well-established mail-order vendors can do considerably better for you—with one major exception, which happens to be the biggest name in mail-order meat. Omaha Steaks (800-228-9055; omahasteaks .com) was founded in 1917 and began mail-order service in 1952. While Omaha pioneered the category, it's not a premium vendor. The beef is a mix of prime and choice, with no way for you to know which you'll be receiving, and the steaks are wet-aged. Also, Omaha ships its meat frozen. That's not necessarily bad (steaks and chops freeze quite well for limited periods), but there's no way to know how long the product has sat frozen in the warehouse. And the company's heart clearly isn't in its pork, lamb or veal offerings, which are pedestrian.

A better option is Allen Bros. (800-957-0111; allenbrothers.com), a century-old Chicago operation that supplies beef to many top steak houses, including the Chicago Chop House, Morton's and Del Frisco's. The good news is that all Allen Bros. beef is prime; the bad news is that most is wet-aged and frozen. Deep inside the catalogue, however, you'll find a decent sampling of dry-aged, unfrozen steaks, which are superb. In addition, Allen Bros. sells high-quality pork, lamb and veal. Definitely a step up from Omaha Steaks.

A further step up, and MONEY's pick for the best vendor on this list, is Lobel's (877-783-4512; lobels.com), the mail-order arm of New York's most venerable butcher shop. Lobel's beef is the primest of prime, is never frozen and is dry-aged for four to six weeks, instead of the usual three. Lobel's other meats are similarly outstanding, especially the Kurobuta pork, a premium breed with more extensive marbling and juicier flavor than most American pork. And Lobel's 24-hour customer support is the best in the industry. This isn't just a mail-order butcher; it's a true gourmet meat operation.

If you're willing to splurge, Lobel's and Allen Bros. both offer super-premium Wagyu steaks—dry-aged in Lobel's case—which come from the same breed of cattle used for ultra-tender Japanese Kobe beef. This is some of the best beef you'll ever taste—and at $100 a pound, it should be—meltingly tender, with a distinctive mineral tang.

Another intriguing option, especially if you're uneasy with factory farms, is Niman Ranch (866-808-0340; nimanranch.com). The Oakland company provides high-quality meat to restaurants, specialty markets and now mail-order customers. All Niman Ranch meat is antibiotic- and hormone-free and raised on small, environmentally friendly farms.

Interestingly, Niman Ranch doesn't submit its meat for quality grading (the program is voluntary, much like movie ratings), in part because the company believes that its farming practices trump the grading standards. As Niman's website explains, "Grading measures the amount of marbling at one specific cut in the carcass. We believe great taste is...the result of a combination of feed, breed, age at the time of slaughter, care and handling."

They're essentially asking you to take a leap of faith, but the proof is in the product: Niman's unfrozen, dry-aged steaks are almost as good as Lobel's. And the extraordinarily juicy pork will be a revelation if you have forgotten how good pork tasted before the industry started breeding superlean hogs. Just make sure to check the package carefully—this stuff is so good, the FedEx guy might keep a pork chop for himself.

If you don't live near a gourmet butcher, these three outfits are your best options for seriously delicious premium beef. For comparison's sake, the sample orders below are for strip steaks—but each of these operations offers many other choices.