I started off official grown-up road bike life with a gifted (for helping a family move out of state) 51cm '85 Schwinn World Sport, and have slowly explored nicer and nicer tubesets and components since then. The Prestige stuff has only been on race bikes, so I/we have to look at tubing on the touring bikes.

For comparison, I've built and ridden an '84 Miyata 610 (DB cromo, hi-ten), an '82 Miyata 1000 (DB cromo throughout), an '81 Trek 710 (DB 531 throughout), a '74 Paramount (DB 531 throughout), and a pair of Cannondale STs. IMO, the ST is well within its right to be considered among the top-end tourers. The Cannondale's front end geometry lends a certain grace to the way it handles and steers. In that regard it would be most similar to the Miyata 1000. The Trek and Paramount have more neutral steering but both have Cadillac rides. The ST with its aluminum frame is obviously tauter than any of the steel, so it's ready to move when you really want to, but the long wheelbase ensures an even keel in normal riding conditions. There's plenty of comfort to be had in its ride.

All that to say, you aren't giving up anything with an ST provided it's set up with a nice saddle and tires (the same way it'd be with a nice steel touring frame) and the fitment measurements are ideal for you. I should mention that all but the Miyata 610 I used the same tires (Conti Ultra-Race folding 700x32s) and almost all of them the same rims those tires mounted to. Fairly apples-to-apples, IMO.

As for the build up of the likely-a-Sirrus, I will probably take parts off my '85 Paramount (gasp!). I never weighed the Paramount's frameset (not super light though) before, and it's the same size as the Sirrus at 62cm CTT. I know the Paramount's ride and handling qualities, and I do like them, save for the less playful nature out of the saddle (Impulse and Prologue have shown me the light there). So it will be a not-simultaneous "Battle of the 62s." I have a 70-72° angle 26.0mm stem currently on the Paramount, and it angles down even with the Paramount's 73° head tube angle. With a 74° head tube angle, I may have to switch stem and/or bars because as much as I'd simply like to swap everything over in one easy swoop, I refuse to compromise the aesthetic, especially if I end up liking the bike that the parts are now on. Do it right, once...unless the plan is a super rough draft for single-issue testing (like canti brake power and quietness, which I've stalled on doing with my '91 Cannondale ST).