You could definitely take off your current technology and swap it for a standard that's been outdated for quite some time that is harder to work with and has less options for upgrades, but why would you? By the time you pay for a new fork, headset, stem, and (likely bartape if it's a single bolt clamp), you are probably coming close to the cost of the bike. Is it just an aesthetic thing, or do you genuinely believe that quill stems are better? I say leave it alone, or get a stem that will work with your current setup but is the proper angle/length for your needs.