You should be fine with any tiller up to 48" in width designed to fit a subcompact. I'd even bet that most tillers that size will fit a BX even if they weren't specifically designed for a limited Cat.1 hitch.
And, I'll repeat what I've said many times before... BX's have PLENTY of horsepower for their size, even the 1500 model. You will run out of traction LONG before you run out of power.
Even if the going gets tough there are things you can do to maximize your power utilization:
1. Reduce your forward speed. It shifts more power to the PTO (because less of the available power is going towards propultion) and at the same time relieves some of the load on the PTO because the tiller is taking smaller bites.
2. Take less-than-full-width passes. You are effectively reducing the width of the tiller by subjecting only a portion of it to hard soil. The rest is just re-tilling soil that has already been broken up.
3. Make multiple passes. Go shallow at first, then work deeper.
4. Dampen the soil first to soften it up. Wait until after a light rain or set a sprinkler on the area. But let it dry out a little before you get started so you don't get stuck.
Obviously these suggestions don't apply to a big operation, but for the homeowner and hobby-farmer it makes a lot more sence than spending thousands $$$ on a bigger tractor that you really don't need.
