<font color='#000000'>I just considered mid-fi to be the high-end consumer grade equipment, while the more esoteric brands are hi-fi (you, know...the kinds of equipment you only find at small stereo shops, the shops that usually sell planar-magnetic speakers and $300 interconnects).
To me it's not a separation of fidelity really, I'm just abusig a term slightly to refer to it's ease of acquiring. It's always far easier to go to circuit city, Fry's, Good Guys, HH Gregg or whaerever and picking up a Harmon/Kardon, Yamaha, or Onkyo as opposed to Sherbourne, NAD, Aragorn, or any of the other "hi-fi" brands.
Honestly, I do feel that the mid-fi hi-fi rift goes all the way across the board. I have seen low-cost speakers blow the doors off of far more impressive looking, and wel known speakers, as well as with other gear. so to me it's all a matter of how hard you have to look to get one.
low-fi: any component under $100, typical gloss black plastic finish, amps freq res. starts at 40hz, cd changers often use car-style cartidges or multiple trays to load from. Sometimes the DVD player is integrated to the reciever or even found as a "home therter in a box" system. This is the most common type of large audio system found in a home. Some shelf systems fall in here as well, with a very small percentage making it to mid-fi (hint: this brand often comes with properly made and well-known speakers, not some cheap thing made just for that system)
mid-fi: Any good quality component that is readily or somewhat readily availible, often has excellent price/performance ratio, and good to excellent build quality as well. Less common than low-fi, but the brands are still well known.
hi-fi: should be called hi-end more appropriately. Often focuses on every little detail, top-notch build quality, internals are often of hte best materials. The audio equivalent of a exotic-car buff. Equipment can be slightly expensive to outlandishly expensive (starting from a couple grand to upwards of $40k plus). Often found in specialty audio shops, and various online retailers. Most likely you only know a handful of people if that in real life at most who owns equipment in this category. You fall in this category when you tell someone what you have, and they give you a blank look until you say "It's a really expensive stereo".
At least that's my scale for what falls under what category.
Yes I do know NAD makes a DVD/Receiver combo, they are an exception to the rule however.</font>