Well, there are tons of options.
But the biggest factor in all this is the price..
The whole 2-stroke issue.. Its not hard to maintain a 2-stroke. You think it is, until you get one and realize that it really isnt any big deal at all.
A Kawasaki KDX 200 is what I have, its a 2-stroke offroad bike. I think its the perfect bike. But then again, it retails for 4000$ but can be found a couple years used for about a grand less.
However, You say you learned on a CRF-230, and you were tippy toing it, then a KDX might be a little too big. But then again, you will have to learn to grow into it. Some people like their bikes a little small to begin with, but the biggest problem with that however, is that once you master the bike, you will wish you have gotten bigger..
Otherwise, If your looking into a 4-stroke offroad bike, Hondas CRF-150 might be a good tiny step down from that 230, and I would also look into the Suzuki DRZ 125, Yamaha TTR 125, and the Kawasaki KLX 125. They are all fantastic bikes.