The Jamis Quest should clear 28s with fenders and is fairly light, though it does have a carbon fork. I've been trying to find out if it'll still be around for 2014; I read that Jamis is bringing all their steel roadies under the Quest name and I'm hoping they don't bring down the high end with this change.
Soma's and Surly's were mentioned upthread. I have a Soma ES which is their road-sport frame. My size 60cm frame weighs 2109 grams (4.65 lb). The IRD Mosaic 57 carbon fork which is often sold with the ES weighs 536 gr (1.18 lb). Together they retail for $650 but can be purchased online for significantly less. I built my ES up with a mix of old, new, and NOS parts including a fairly light wheelset and, as equipped below with Honjos, weighs 20.25 lbs. Tire clearance is 28mm w/fenders, 32mm without. I'm in for much, much less than the OP's budgeted $2500.
How about this 'off-the-rack' Tricross from Specialized.
Tiagra components instead of 105. 'External' 68mm bottom bracket (Hollowtech or ?), disc brakes, comes with 32mm tires so should be able to take 28's, and rack & fender mounts. This is the end of the 2013 model year, so you may have to call round and see if ny are still available, or wait for the 2014's to come out and hope this model is still around.
Mine is a touch heavier at 24 lbs but I've got heavier wheels (Mavic Open Pro) and a rack. I run size 32 Grand Bois Cypres tires.
Have you looked at;
These are not in stock yet, but I'm looking at using my employee discount on one of these (pending a test ride of course). GT Corsa Disc - (some) 105 components, steel frame, carbon fork, disc brakes, large tire clearance.
There have been some recommendations for the SOMA ES. I the lugged version that I am building up as a light (compared to a Bruce Gordon R&R) touring bike.
You can see it at http://indianbendsolutions.com/stany...namo-lumxos-u/ with component listings.
For a steel road bike, Soma offers a number of different models at attractive prices. Plus they're nice bikes. I love my Soma Double Cross. It has been my main go to bike for ten years.
If I were going to buy a steel frame that's not a boat anchor I'd look at something like a Pegoretti Love #3 . You can easily build one of these up under 15lbs. For randoneuring under 18lbs would be a piece of cake. That's what my Colnago weighs.
How much does a boat anchor weigh?
If you asked your question in the C&V you'd get lots of suggestions. Just saying.
I just mentioned C&V because of the OP's stated desire for steel. Good, lightweight steel bike of all sorts are the bread&butter of the C&V. Not necessarily expensive either.
But the boat-anchor constraint could be an issue. My Masi is 23lbs ready-to-ride, not with necessary items like pedals removed. Is that a boat anchor? Maybe.
I don't think there is any need to go with a 20+year old bike, unless that's what you are looking for, when you can get a very light modern steel bike. There is lots of good stuff out there. As far as what's a boat anchor goes, anything over 18-19lbs for a long distance bike is getting porky in my book. ;)
When you are talking bikes you are correct that you are really talking a "package" in which the frame is just a piece of the puzzle. The Pegoretti Love #3 that I mentioned earlier is a steel bike that can have a ready to ride weight of less than 15 lbs (including pedals). My friends bike that he used for RAAM this year was right at 15lbs. My bike was less than 25lbs fully loaded (including water bottles) at the start of the last 1200k I did. Long distance bikes can be quite light.
What it comes down to is what you, as the rider, are willing or wanting to do with your ride. Some people would be very uncomfortable starting brevet on a sub 15lb bike. For me, I want to carry as little extra weight as possible while retaining reliability. Therefore my long distance bike is a few lbs more because I'm using slightly more robust components. Either way, I'd consider a 20+lb bike porky. ;)