What frame(set) am I looking for? (Outside of my narrow Columbus world)

...it'd only get nicked.
Nothing wrong with "showy", I was getting at what you will actually use the bike for: Sunday best, commuting etc.

Apart from those you mentioned, look out for Daccordi, Zullo, Cioc, Somec and Gios; they all offer the sort of quality you're after. Some gems outside of Italy.

There aren't too many companies making steel: as well as Reynolds and Columbus the ones I can think of are Mannesmann, Oria, Ishiwata and Tange. A little time spent trawling the internet and you will soon be familiar with the different grades and able to make qualitative judgements.

Lugs are more likely to be an indicator of quality, than weight: nicely detailed, hand-filed lugs take time and skill, but lugs are a pretty stock item.

Seat post diameter is a more useful guide to the likely weight of a frameset: 27.2mm will be lighter than 27.0mm which will be lighter than 26.8mm etc.

Dropouts are always worth a look at: no-one puts Campag ends on a BSO.

Internal cable routing can be a red herring: sometimes used to give cheaper frames, a more expensive look. Look for a tube brazed between the two holes in the top tube.

Framebuilders like to show-off around the junction of the seat stays and the seat tube and in the way they finish off the seat stays. Have a look at frames you know to be top notch and compare with cheap ones.

I like a nice brake bridge! A tube with a hole is as basic as it gets; a shaped (often square where the brake attaches) is nice, but my favourites are the shaped pieces that look like an upside-down, lazy "V".

By no means exhaustive nor without exception, but it should get you started.

...that'd be nuts for an all-weather weekday bike.
As is everything you so far want. :)