Welcome to the forum!
You're comparing two fairly different guitars...the F11 is a folk size guitar, a much smaller body style than the WD32SCE, which is a "dreadnought" size guitar. The difference in tone between the two that you describe can be attributed to the size differences of the bodies, or perhaps the materials used in the construction. The WD32SCE has a solid-wood soundboard, whereas the F11AN has a laminate soundboard.
As for the F11AN string issue, it is usually possible to go up or down one "size" from the standard size strings without needing a new setup....almost ALL Washburn acoustic guitars come with light gauge strings standard. If you were to replace the light gauge strings with mediums you could expect more volume. If you go up more than one gauge size you COULD have issues with the neck needing to be adjusted to accommodate for the increased tension, and perhaps even have difficulty with the strings fitting into the slots on the nut, the piece that holds the strings up off of the fretboard at the "top" of the neck.
A personal note...I owned a WD32S for a while. I really regret giving it away now. It had a gutsy tone that my all solid-wood equivalent WD32SW doesn't have, and it was VERY happy being played vigorously. I'd buy another in a heartbeat if I could.....and I don't really like the bigger dreadnought body style. Not only was it my first Washburn, it is one of my most memorable.
Good luck with the decision...spend some time with the WD32SCE if you haven't played on a dreadnought much. They are a large guitar if you're use to the folk size body style...not everybody's cup of tea, so to speak.