Go touring first, before you spend so much on one of those bikes. There may be some things you'll want to have some forethought about, but try not to commit to spending over a thousand pounds without any experience touring when you could probably tour a few weekends or a week on what you have now and get a lot better idea of what you want.
If your current bike is totally unsuitable for even a weekend touring, get something used and depreciated. Used Trek 520's sell for $400 to $700 around here if they're at least 5 years old. The thing is, after you tour on it the rest of the summer, you can sell it next spring for the same thing you paid or even more. The same is true for any bicycle that's at least of some vintage. You don't want it to be so old or worn that you'll have to upgrade it before using it though. The only thing you'll have to pay for is a brand new bike or any upgrades.
"Touring" means different things to different people. Some people seem to think you need a transcontinental expedition bike to tour. I like to go for a couple hundred miles and some people might consider that a day ride, but I take everything I need with me for a few days of living, eating, camping and so on and if there's a hostel or hotel on the route I will probably enjoy that for one night to get a shower and soft bed, but generally I would prefer to spend on food than hotels. The load you actually end up taking with you in terms of bulk and weight will determine some things about what bike will work well, and what luggage will hold it all and what kind of bike and racks that style of luggage fits, and then there's the kind of terrain you'll ride which might inform your tire and gearing choices.
The ideas in your imagination about touring are one thing, and your actual experiences are another. Working things out through some experience will get you closer to reality than your imagination, and the best way to do that is with your current bike or another one that's already depreciated.