Originally Posted by RaleighSport

Not always, I saw you got a lot of explanation as to why you'd move fully to a newer group so my advice is going to swing in the opposite direction. At 6 speed, you're pretty much assured you already have the dropout spacing for 7 speed, shimano currently makes 7 speed brifters (they're on the low end of the spectrum) that work very well, assuming your drivetrain is already shimano 7, that means you'd just need the STI's and the STI barrel adjusters (can be had for just under $100(USD) new. Assuming you have 6 speed, odds are it's a freewheel and you can simply pull it and replace with a modern 7. If it were my build and I didn't have "quality" FD/RD, I'd look into a set of Shimano Tri-Color 600(Ultegra) Derailleurs, which can be had for fairly cheap and perform amazingly well and will play nice with modern 7 speed STI's.