All the sponsoring dealer on CGN are pretty picky when it comes to what they decide to bring into Canada, so you can't go wrong with any brand of product they choose to sell.
Out of all the parts that makes up an upper, the barrel is the one that will have the biggest effect on performance, which will take up the biggest share of your $1000 budget, Alberta Tactical makes custom barrels in 5.56, .223 and 223 Wyld, but they start around almost $600, than next item will be the rail, which is all personal taste it can pretty much take up what is left of your budget.
To stick to your $1000 range I would look at RRA or Arms East and Questar's house brand uppers.