Though it was a relatively modest opening by the company standards - just south of the million-dollar border - Stephen Starr's Mexican makeover for an old dive-diner (the Midtown IV) still bore unmistakable traces of El Conquistador's macho glitz.

Dowdy formica counters and grotto-stone walls have been kitsched-up with lacquered Mexican movie posters, velvet Elvises, and bedazzle tiles. The old Naugahyde booths got a lowrider flourish with golden embroidery spelling out "El Rey." Starr bragged with his usual "Philly's never seen anything like this before" bluster, touting the hideaway Ranstead Room cocktail lounge at the back of the building. Above the gold-painted brick facade, meanwhile, a marquee bears the bold Spanish promise: "esto cambiara su vida" - "this will change your life."

No, El Rey will not change your life. Unless, of course, you live in Rittenhouse Square, where a genuine mole or braised baby goat had once been tricky to find.

But the big picture is this: For perhaps the first time in Starr's storied career, his latest restaurant - Number 20 on the active list - will likely make no significant impact on the wider restaurant scene. It's not a trendsetter. It doesn't mark a new standard for an existing genre. The design has no compelling draw - save for the undeniably groovy cocktail lounge hidden in back. And the whole operation shows inconsistencies (from service to the bar, which made a pitcher of margarita so sour and bitter we couldn't drink it) that feel like the stretch marks of a company overreaching.

And unless you have a 25-year-old's tolerance for the supersonic boom of a tequila-fueled noise chamber, don't bother coming on a weekend night. We learned the hard way when a bachelorette party settled in (with a blow-up doll) at a long table beside our cramped little back booth and knocked the decibel meter, already hovering in the mid-90s, up to 101.

Why, I wondered upon exiting to the quiet of Chestnut Street, would I ever return?

During the more civil moments of weeknights, brunch and lunch, chef Dionicio Jimenez gave more than a few good reasons. The former Vetri chef made his mark at Xochitl, where he riffed on his Mexican youth with inventive, modern upscale dishes.

His mission here is less creative: to produce a menu of affordable, authentic street food. The idea isn't to rival Starr's more "nuevo Mex" El Vez, or, for that matter, Jose Garces' Distrito (and it doesn't), but rather to bring a genuine flavor more in line with South Philly's taquerias to an uptown setting.

The prices, with most big plates around $15 or less, are reasonable. And while there are a handful of unexpected stumbles here - a bland, lumpy guacamole, a meanly oversalted garlic shrimp - Jimenez also turns out some marvelous handcrafted dishes that I've been savoring in my mind ever since the eardrums stopped ringing.

The tortilla soup, poured tableside into a haystack of shredded tortillas that half-soften like noodles but still retain crunch, is redolent of earthy pasilla chiles, herby epazote, and a porky echo of chicharrón croutons. Pliant handmade corn tortillas form the canvas for some excellent taco fillings - tender pork shoulder carnitas braised in cinnamon, star anise, Coke and beer; or simply grilled halibut topped with avocado butter; or the Arabes lamb tacos, braised Puebla-style with avocado leaves, rosemary, bay, and clove, then finished to a crisp on the grill.

Memorably fluffy tamales came two ways, oozing cheese from inside a corn-husk wrapper, or filled with tomatillo-tanged chicken inside a Oaxacan-style banana leaf. Grilled skirt steak marinated in garlicky anise, nutmeg, and allspice is put to myriad good uses, whether fanned over puffy masa sopes with a poached egg and chipotle salsa for brunch, or atop an emerald mound of chilaquiles, tortilla chips tossed in zippy green salsa that penetrates just enough, but still leaves a delicate crunch.

There were some forgettable moments, like the boring nopales salad, the meek chile accent to my huitlacoche quesadilla, a vaguely fishy crab ceviche, and a first-visit guacamole that was whisked so loosely, it was sloppy and oversalted. I'm also no fan of ropa vieja beef served cold on a tostada - though it would have been smarter for the plaid-shirted servers to advise us the chef intended this as "beef ceviche" before we sent it back (twice) for reheating, and not very successfully.

But Jimenez's successes far outweighed those goofs, from the fantastic quesadilla filled with squash blossoms, corn, and fresh epazote, to refreshing Campechana ceviche brimming with tender shrimp, to a terra-cotta crock of tender baby squid lavished in roasty red guajillo-tomato sauce. The chile en nogada remains one of the chef's homey signatures, a spicy poblano stuffed with ground beef, nuts and dried fruits, then glazed in creamy white walnut sauce striped like a Mexican flag with pomegranate seeds, walnuts, and chopped herbs.

Jimenez's most powerful dishes, though, emerge from the slow-braise, like the meltingly tender baby goat steamed inside banana leaves with guajillo, avocado leaves, and cumin, then served with soft tortillas alongside black beans and guacamole. His trio of moles, though, may be this menu's single best reason to traverse Broad Street or the Schuylkill, with each shade of sauce revealing a different, complex personality. The pumpkin seed-orange pipian glazes tender pork ribs with a warm balm of guajillo heat. A cinnamon-hued mole Poblano bathes chicken with the tingle of Mexican chocolate, almonds, raisins, and the smoky tang of tomatillos and chipotles. Midnight-dark Oaxacan mole negro, meanwhile, matches the intensity of gamy lamb with roastier dried peppers, mint, thyme, and a deep fruity undersweetness of prunes.

Let that sweet-and-savory thrill linger - because, oddly, there aren't many desserts to choose from, save the usual spicy chocolate ice cream, some so-so churros served with thin goat dulce de leche (where's molten chocolate when you need it?), or a salted lime sorbet that tastes like a better frozen version of El Rey's margarita.

Best to call it a noche, and head back to the Ranstead's cozy booths, soft lights, and classic cocktails, where, truth be told, Starr's vision shines brightest.