I'm not an electronics person, just an RC hobbyist. I was going to suggest a simple BEC (Battery Eliminator Circuit; typically a switching, not linear, voltage regulator) for powering the receiver. It would take the input voltage down to 5V, 6V, etc. Something like this:
eBay auction: #http://www.ebay.com/itm/HOBBYWING-RC-UBEC-5V-6V-3A-Max-5A-Lowest-RF-Noise-BEC-/221588340456?pt=Radio_Control_Parts_Accessories&hash=item3397b1bee8But that adjustable one you posted is even cooler! And it's great to know about, for an unrelated little project I have in mind, thank you! Cheap, wide input range, and adjustable output voltage, perfect
If it's draining an AA battery in about 10 minutes, the current draw could be somewhat high? An NiMH AA is often around 2000mAh. If we assumed you really drained the whole battery in 10 minutes, that would be 60min/10min = 6C draw. 6C * 2Ah capacity = 12 amp average draw (I've never tried to pull a lot from an AA, I'm skeptical they'd be able to put out 12A)? But even if it's only half that, that's still 6A.
If using some sort of converter to power the motor, you might need to consider the amperage rating of the converter. Or check the draw of the car.
And if you really want to make a difference, going to brushless and maybe a 2S LiPo would do it!