The Parkzone T-28 seems to be very popular as a second plane if you want to get into something more aerobatic and has that warbird look.  Sounds like a good next plane for you.

You can also go to electric gliders and go for a completely different experience.  That is what I did, I went to gliders rather than bigger, faster more aerobatic birds and never looked back. Gliders is what I fly most of the time now.

So, where you want to go is what will show you the path to your next plane.