Awesome!!
Hope to see some pictures of your build as well! Servos are expensive no doubt, I got a used set I found online that are 100% overkill. A $70 servo is the baseline price for a Metal Gear, Digital, Coreless, High Torque Servo. It really depends on a couple main factors: Flying style and Battery Voltage 6.6 or 7.4/8. Running a gasoline engine, you'll want Metal Gears that are capable of 200+ oz/in, everything else depends on the budget. The A6320 is basically a 250oz/in servo @ 7.4V and is brushless for $80... it's actually not bad.
With all that said, What batteries will you be using? What price point are you thinking of? Are you considering a Powersafe Receiver?
Not a bad way to go for Coreless, and is good on 6.6V and 8V, super fast, enough torque and $10 cheaper than the A6320's
http://www.promodeler.com/coreless-servos.aspx
If you want to use a brushed servo, they are cheaper... draw backs are longevity and efficiency. BUT the price is $45-50 each
Cheaper, 3pole, enough torque at 7.4v, digital:
http://www.promodeler.com/DS270DLHV
Cheaper, 3pole, lots of torque even at 6.6, digital, a bit slower:
http://www.promodeler.com/DS360DLHV
Savox makes some great servos for 6V if you are using a LiFe/A123 battery setup. BUT with so many servos working, and long runs of wire, it is good practice to run a higher voltage, and they are still in the $70 range. SA-1256TG comes to mind. I've heard of people having issues with powersafe receivers and savox before.
I could keep listing servos forever, but the fundementals of what voltage, budget, and style are factors that need to be determined. Overall, I don't think you'll find a Digital Coreless/Brushless servo for much less than $70, You'll have to go with a 3-pole motor or used to save the piggy bank.