building a bike up from parts is generally more expensive than getting a complete. I feel like a $1000 build budget will probably get you wheels pretty close to what you've probably already got stock, unless you're good at shopping around or waiting for sales. If there's nothing wrong with your wheels you got why not just ride them until you either find an issue you want to upgrade on or they need proper replacing.

seems like you're going about it backwards. rather than having a reason to upgrade then finding your budget, you're trying to pinpoint a price point for a part you want to upgrade but don't know what you want exactly.