First off, I'm a big fan of *old school* stuff. I like friction shifting, 21 gears of less, real leather saddles.....but I do believe that threadless headsets are much better than the old kind. Buying a new steel fork/headset/stem is cheap ($100 or so?) but it's a worthwhile upgrade. Touring bikes, because of the loads carried on the frount rack, need a good headset.

With that said, If I was in your shoes, I'd be keeping the threaded one, looking for a cheap used quill stem and saving the money. It will still work.

Good luck with the new bike and remember if there is trouble with it, you can fix it way cheaper than a new bike.