Looks like I missed something when I was typing up my last post. I missed the question about 8 channel systems. The $250 Futaba 6K V2 is actually an 8 channel system that you can look at here:
https://www.towerhobbies.com/product.../FUTK6100.html
Spectrum has four 8 channel systems to choose from:
As you can see, with all but the most expensive Spectrum, you also have to buy a receiver of which Spectrum only has two 8 channel choices:
There are more 6 channel options as well, if you want to go that route. You would also have to get a receiver battery pack unless you are running an electric motor with an ESC that has a battery eliminator circuit to power the receiver and servos. Some of the transmitters I listed above come with rechargeable battery packs, some use AAs, something else you need to look at