Classic & Vintage - should I modernize my 87 Schwinn Circuit?

Not so long ago I picked a frame from the rafters from one of my lbs. My original intentions were to make it into a fixie, which I did. I have been happily riding it along this way for several months now. But lately, I have been getting the itch to build it up into a geared bike. however, I don't want to use retro components, I really want to use modern sti style shifters and brakes.
So I wanted to get some opinions from the forum.
As the title says, I have an 87 schwinn circuit. Its made from some columbus steel and fits me very well. I would still like to keep it on a budget, so I have been thinking shimano 105 would be adequate.

Not so long ago I picked a frame from the rafters from one of my lbs. My original intentions were to make it into a fixie, which I did. I have been happily riding it along this way for several months now. But lately, I have been getting the itch to build it up into a geared bike. however, I don't want to use retro components, I really want to use modern sti style shifters and brakes.
So I wanted to get some opinions from the forum.
As the title says, I have an 87 schwinn circuit. Its made from some columbus steel and fits me very well. I would still like to keep it on a budget, so I have been thinking shimano 105 would be adequate.
The Circuit is a great bike. I wouldn't hesitate to update the components if it were mine.

It's probably got 126mm rear spacing, so if you want to put a 9 or 10 speed cassette on it, you might have to cold set the dropouts and rear triangle spacing.

Barcons and a 7-speed freewheel would be an economical combination which would still permit gear changes with both hands on the bars.

I've done a similar project with my Miyata Seven Ten. I'm running a 130mm rear with 8 speed gearing. I'm actually still using the Suntour Cyclone stuff (no problems with it) and running friction. I guess it's a little metro-retro!

I think the used 8 and 9 speed Ultegra can be found for good prices and might be a good way to go. I've heard good things about the new 105.

I have an early '86 Schwinn Circuit myself and have been researching some upgrades. Less wheels, Ultegra 9spd can be done for less than $250 using Dura Ace 10spd downtube shifters. It'll keep some of that vintage feel/look without the brifters.