If you are going to let the fact that the PT425 or others have the Subaru in them, and are waiting for the company to put another engine in it, you might be waiting a long time.
I Can't say I am a fan of the Subaru, but I bought mine back in March and it started fine down to 30 degrees. (I will put a heat pad on it before this Winter) but I looked at many other machines, and you get what you pay for, and don't think there is anything in their price range that comes close.
To this point I have had no issues with the vapor lock, or other problems many seem to have. True, I don't have but 60 hours at this point, but so far I am happy with the machine.
True, I don't mow with it, but that is not why I bought the machine. Too many cheap mowers out there for grass only, and I use a zero turn on my lawn, of which I decreased my mowing time by about 2/3 the time over a 50" John Deere. It just goes faster, will get closer to things, and does a over all better cut.
The starting problems in the cold could be due to the small starters, or it not getting enough amperage. I know that an Onan I had in a John Deere would have problems also, but there was a relay kit you put on them and never had these problems.
To me the design of the engine down in an enclosed tub on three sides is going to be hard for any engine to keep the coolest, and I have done the fan, header, exhaust and other mods, and so far am pretty happy with the machine.
Just my two cents on this.
Moss, Are you the only one on this Power Trac forum with a Kohler? Everything you just stated I completely agree with. I am ready to purchase a new 425, however my experience with my 422's Subaru. I just can't allow myself to pull the trigger because I know I will regret it. I call Power Trac every so many months asking if they can put a Kohler in it and they say they can't because they aren't Kohler dealers.