I agree 100% with what 5030 posted.
We purchased one of the newer TroyBilt tillers, and then I recently inherited one of the older models. I have a love/hate relationship with the newer machine. It does a good job under good conditions, but it isn't heavy enough on the wheels to keep the tines from occasionally suddenly propelling the machine forward when the tines hit hard soil or a clump of weeds. When I inherited the older machine, it made the newer machine look like a toy.
The older machines are still out there, and parts are available including replacement engines (no-brand engines for as little as $75).
I researched buying a Simplicity before I got the older TroyBilt, and found parts for them, but the availability was not as widespread as for the older TroyBilt machines.
If you are mechanically inclined, buy an older machine and "fix it up".
If you're not mechanically inclined, go to a local small-engine repair place and ask them what they recommend.