Congratulations on almost popping the question. Serious love I take it then.
For something very inexpensive...Everest on Queen/John. I've never spent more than $100 for 2 there with wine, tax, and tip. Nice atmosphere, but perhaps you want something more upscale.
For places near Yonge, and downtown. I would say Splendido ($400), George ($400), Oro ($250), Nota Bene ($200), and Canoe ($250).
Of these places, I would say Nota Bene, or Canoe. But...if you're willing to go just outside of downtown. Avenue and St. Clair. There's my favorite restaurant, Scaramouche. It sits on a hill, overlooking downtown. Honestly, it doesn't get more romantic than this. Great food, desserts, wine list, and the best service imo in the city. $250 for 2 apps, 2 entrees, 2 desserts, and a decent bottle. Tax and tip included. As well, there is the Scaramouche Pasta Bar and Grill. It shares the same space, same atmosphere, and service; but the menu is different, but still great. $150 for a dinner for 2.