This is a great mic. I got it in my mail just over a week ago. I've done many tests with it, and the crispness of the sound keeps surprising me. It's an amazing microphone for the price. My only gripe with it, is the cheap windscreen that comes with it. It's completely useless! I'm going to build a mic blimp soon enough though. From the testing I've done, and the reviews I read, the AT897 is one of the best microphones for this price range.
I don't have a beachtek. I use an XLR to mini converter cable. I cannot complain at all. The cable does what it's supposed to do. No problems. No interference. Everything's perfect. My only gripe with this set up, is that i cannot control the microphone volume settings at all. If you don't have manual volume controls on your camera, you might pick up unwanted sounds, simply because of how sensitive this microphone is. It's nothing killer though, and nothing that would put a dent in your dialogue. I really haven't gotten to the point where I need a beachtek, and I doubt I'm ever going to buy one. Though if you're OCD about your sound, want two XLR ins, and full control over your audio on the set, a beachtek is he way to go.
For the cable: Any monster XLR cable will do. A 20 foot cable will go for 10 bucks on ebay. Or you can go to any music store and buy yourself some cable. Buy as much as you'll ever need. It would really suck if you were on set, and realized that you don't have enough cable length to do the shot you want. Excess cable can be annoying, but it would pay off in the long run.