There was a time when one could tell "luxury" cars from their "entry-level" siblings by their labor-saving devices and omigosh electronics gear.

Luxury cars had automatic transmissions, power windows/door locks/outside mirrors, cruise control, and stereo/cassette systems with more buttons and switches than a sound studio.Entry-level cars had four on the floor, manual everything and an AM radio with a couple of knobs.

No longer. The distinction between the top and bottom-of-the-line cars has been blurred in recent years and the 1991 Nissan Sentra has virtually erased it in all specs but one: sheer size.

The new Sentra is the final link in a chain of high-approval cars that Nissan has been forging over the past three years. In the time that many carmakers take to redo the fenders and grill of a single model, Nissan has completely redesigned the top-end Maxima sedan, the macho 300ZX sports car, the 240SX sportster, the mid-line Stanza, and now the least expensive of the line, the Sentra.

The '91 Sentra isn't just a "freshening" of its predecessor, it's the result of a clean sheet of paper - or a blank computer screen if you're the high-tech type - and it's just now beginning to trickle into Utah Nissan dealers. The folks at Rick Warner Nissan let me take a "cherry red pearl" Sentra GXE for a couple of days and I am once again amazed at what Nissan has wrought.

Following a pattern set by Maxima and Stanza, the Sentra could stand as an entire car line by itself, never mind a single model. It includes the E, XE, SE, GXE and an affordable two-door nickel rocket called SE-R that has its own 140hp engine that revs to 7,500 rpm and is so much fun to drive it's probably illegal (in fact, driving this car the way it's meant to be driven is definitely illegal.)

I took a quick run around the block in the SE-R but I did my serious evaluation of the GXE. This model is the top of the Sentra line, a luxury four-door sedan with a deceptively voluminous trunk, all the power goodies that used to be found only on Cadillacs and Lincolns, adequate acceleration, great handling, understated good looks, immaculate fit and finish and 29 to 39 mpg depending on whether you drive like an outlaw or a solid citizen.

Nissan probably wouldn't appreciate this, but all the time I was driving the GXE a question kept occurring to me: Why pony up thousands more for a Stanza or Maxima (or any other more expensive car for that matter) when the Sentra offers so much for so comparatively little? (msrp $8,329 to $11,200 depending on the model and options.)

The obvious answer is size. Despite its manifest charms the Sentra shows its econobox roots in its somewhat confining quarters, especially in the rear. I'm only average height, but without moving the driver's seatback forward, I literally could not get in the back seat; not enough knee room. My kids thought the rear seat was just fine, but I wouldn't want to test that on an extended trip. I don't have to get anywhere that badly.

So, if a roomy back seat is a priority, you will probably want to move up to Stanza or Maxima; otherwise, buy the Sentra and take a Caribbean cruise with the money you save.

There is, of course, the question of status and prestige. If everyone were content to buy a car that simply got them comfortably from point A to point B, then the folks at Mercedes-Benz and their megabuck counterparts would have to find another line of work. Sentra won't win you many points for conspicuous consumption.

I have one nit to pick with the Sentra. The warning buzzer that nags about seat belts left unbuckled, doors left ajar and keys left in ignitions was the most rasping, ear-offending, annoying such device that I've heard since the very first ones were installed in cars back in the '70s (when you could just reach under the dash and rip them out).

In an age when most cars emit a pleasant chime or electronic beep, here's this otherwise quality product with a buzzer that sounds like a 15-year-old rusted out Fiat. Nissan, I know it's a small thing, but you really blew it here: lose the buzzer. Please.