The Futabas sell for around $70 on e-Bay.
Hobbyking has Orange and Corona, I have plenty of flights in those, never had a problem. Can't beat the price.
I like these a lot:
http://www.valuehobby.com/radio-syst...receivers.html
I only use the Futabas I have in the more expensive planes, but the 'cheapos' are definitely a good choice.
As far as the batteries go - there is no need to use different batteries if they work fine now. Brownouts do not happen until the voltage drops to a
critical level. And they happen with any receiver. Sometimes the voltage just drops for a split second due to a lot of current draw from the servos.
The rx would shortly stop working and you couldn't even tell something went wrong.
The early spectrums had a longer 'reboot' time, the rx was 'out' for a few seconds which lead to some crashes. But this has been taken care of.
I have been using LiFe batteries with a regulator, they are safer then Lipos and can be charged in less then 30 minutes. HK has great prices on these, too.