I have a 23 Kawa on my 52" Encore (shaft drive between engine and deck). It's a pretty beefy engine and it has more than enough power for this size machine. I often mow very thick and sometimes wet turf and no indication of the engine laboring. She runs like a clock.
When I bought this mower I asked them what the life expectancy of this engine would be and they said ± 2500 hrs if you maintain the engine at the required regular intervals.
She now has ± 600 hrs and except for regular oil changes and replacing oil, feul and air filters, I've had only but joy out of it. No leaks, no seapage, no usage of oil - touch wood.
The Kawa is a cold blooded engine and even on a hot summer day you want to choke it to start a cold engine in the mornings. Other than that you show her the key and she'll fire up.
I found the engine noise is a little lower than the Kohler, but heck does it matter what the noise levels are after a day sitting on a mower mowing. A few decibells won't make no difference.