I use a TPH-122 MacKissic on my 18.5 hp JD 4010. I've NEVER bogged it. Have had a Mac on an old Gravely and a stand-alone TroyBilt. I did bog those. Paid about $1700 for mine a couple years ago.
The Mac is a whiz to maintain compared to the old TroyBilt. It's lighter weight, but this seems to help to shed wet stuff with just a little bit of limbing thrown in from time to time.
Think MacKissic makes the DR stuff.
You can get MacKissic through Northern Tool. Our local JD dealer carries them.
Ralph