Quote Originally Posted by k_c_r
If you want something much faster but still want a high level of force, you're gonna be looking at lots of £££ on an extremely high-quality actuator, or custom-built system. The time Nick mentions of ~1 sec isn't really viable with off-the-shelf actuators. It's certainly achievable for a lifter; Storm 2's lifting arm was devilishly fast for an electric system, but no actuator in sight there - there you're talking about a Magmotor running through a custom-made gearbox setup.
Cheapest way to do it right is to use the mechanism from an existing actuator (Acme thread or ideally ball-screw) driven off a more powerful motor: the dinky little motors powering the actuators you stated will only pull ~35w at peak, whereas you could, with minor modifications, use something far more powerful like a DeWalt hammerdrill motor - that'll give you plenty of grunt to lift robots quickly. Feel free to buy an off the shelf high speed actuator for the low gear ratio - but you'll probably need to jam the clutch mechanism on it if there is one so as to be able to take advantage of the increased torque given by your new motor.

Off the shelf actuators that get picked up from Ebay or other surplus sources are primarily limited by the fact they're usually designed to open window blinds, move beds, aim Sky dishes, and such like - therefore they don't really need to move fast and can get away with an itty-bitty motor (run at a very high gear reduction). That's something which can be sorted out easily and without going to the extent of a custom mechanism.