28's and lower pressure seems like the cheapest thing to try. Since I've allowed myself to get out of shape, I've been doing a lot more riding on my late 80's/early 90's road bike (not that it matters but a Concorde Aquila with SLX tubing. It's got a CF fork (though steel steerer) from nashbar and takes 28's (though I'm currently riding 25's - veloflex master 25's at the moment), on wide rimes. It might just be the flex of the 63 cm frame under my fat, fat ass, but it feels super plush. The nice thing about steel from that era is that it wasn't as stiff as the modern steel (but isn't a complete noodle), quill stems allow a lot of height adjustability, and the spacing fits modern wheels/groupsets - I've completely accepted my current fitness and am running a campy centaur triple.
I have also a schwinn voyager frameset (somewhat less agressive, slightly more upright, sports touring frameset that with cantilever brakes that can fit 38's with fenders - sort of like a modern endurance/allroads frame) from that era that I keep meaning to build back up in hopes of starting commuting again and losing some of my gut, but I keep putting it off as I dislike building wheels and I have 2 wheelsets that I need to put together - rims on my steel road bike are about worn out and I have a really nice dynamo front hub waiting for the commuter bike.
About 10-15 years ago, prices for decent steel road bikes from that era spiked through the roof, but they seem to have come back down a bit - but good ones require a bit more looking. I don't think I spent more than $150 for either of my frames (the more recent was maybe 5 years ago), but all the little things like cables, tape, appropriate stem/seatposts easily doubled the price, so yeah wider rubber is a much cheaper first step.