Great sounding close to back wall speakers.

Smaller Dunlavy (SC-IV or smaller) or Duntech (Princess or smaller) speakers will work OK as you mention, you'll lose a little depth and might get a bit more bass than otherwise specified in the measurements but otherwise you can be OK. The best close to wall speakers I have ever heard are the Snell Type A-IIIs, designed to be placed up against the wall and terrific speakers. I think there's a used pair up for sale on the 'gon now. Particularly good with classical music, and good bass extension. Only problem is that they're no longer in production, don't know about how well they can be serviced/repaired.

Have you checking into the Allison speakers which are designed go into corners and against a wall literally. One of their models was reviewed in TAS last year I believe.

My Eggleston Works Fontaines sound awesome at less than 24" from the wall (to the back of the speaker). But you'd have to find a pair used for your budget.