I agree, for a single, versatile walkaround lens, the 15-85 IS USM is hard to beat... top image quality and wider than most (there's a significant difference in two or three millimeters at the wide end of things).
One of the best values in a walkaround lens, IMO, is a used 28-135 IS USM... It's a very nice lens that can be found for $200. A ton of these were sold as kit lenses on 40D and 50D, so it's easy to find them lighlty used and steeply discounted (sells new for around $450) . This is actually an EF lens dating back to the film days and far higher specification than most kit lenses. Rivals the image quality, AF performance, close focusing ability, and IS of the 24-105L, at roughly one fifth the price. It's just not as well built/sealed as the L, tho it's pretty good, Canon USM/mid-grade, which is a lot better than actual "kit" lenses.
The main "problem" with the 28-135 is that it isn't wide on a crop camera.... It's a nice, useful standard to moderate telephoto. If you need wider, pick up an UWA to complement it. A Sigma 10-20mm or Tamron 10-24mm might be found used within the remainder of your budget. A Tokina 12-24 can be found for $400 or so. All three sell new for between $450 and $500.
Of the lenses you listed, I'd consider the EF-S 18-135 the best of the bunch, but I'm not really familiar with the 17-85mm and old biases against that type of lens would keep me from ever buying a 20X zoom like the 18-200.
The current 18-135mm version has STM focus ("ST"epper "M"otor) , which is better than micro motor, but may or may not be quite as good as true USM. Canon has intro'd several STM lenses lately, though only the T4i camera can take full advantage of them (with AF of a sorts when shooting video).
According to your signature, you already have the most affordable portrait lens... the EF 50/1.8.
Have you considered selling off your 18-55, 55-250 and 75-300 to help pay for the replacement lens or lenses?
I hope you enjoy the 100-400 and whatever lens or lenses you get to complement it.