You may find the most romance
at Disney's Grand Californian Hotel, but it's the furthest from your request of being "reasonably priced".
So other than actual Disney resort hotels (GC, DLH, PP), all of which are very nice in their own respects, my suggestions are:
Hilton Anaheim - very nice rooms, many with AWESOME views of the nightly fireworks. Also has room service with great food, a very nice pool deck with large pool and four jacuzzi tubs, and all the perks of a full-service 4-star hotel/resort. It could be right around $110-$120 per night.
Candy Cane Inn - I guess it could be romantic (maybe a little). The rooms are cute, and the property is quite nice with lots of flowers and greenery. I imagine at Christmas time it could look quite lovely if they decorate it up. The rooms have no views, but they have a nice pool/jacuzzi area, a great continental breakfast with lots of selection, and they have their own private shuttle to take guests to and from the parks - no fighting for a seat on a crowded ART bus - a BIG BONUS!
Anyway, it's sounds like a great idea to have a romantic Disney Christmas with just you and your sweetie.
It's a long time until next Christmas - maybe you can save up for the Grand Californian.
