Personally, I prefer to use LiFe batteries for the receivers and ignitions in my planes. I'm not comfortable with LiPo batteries in my gas planes. It's too much of a hassle to remove them every time you want to charge them and I refuse to charge a LiPo battery while it's in ANY plane. If you decide to go the LiPo or LiFe route, make sure you buy a switch that totally isolates the battery when you turn the plane off. I've heard stories of people ruining their batteries because the trickle drain through the switch would drop the voltage too low before the problem was discovered.
As far as servo's go, I don't have any HV servos so I cannot comment on them first hand. IMHO, I cannot see any real advantage in them over a good digital servo running on 6.6 volts. The difference in speed of the HV servo over a regular digital servo is probably impossible for most people to differentiate.
I'd also like to share some advice I've received from a good friend of mine who has been flying planes since the 70's. I'm sure you've probably heard it before as well. It's called the KISS principle. A 50cc plane does not need all of the accessories that you'd put in a 40% plane. With that being said, I would recommend investing in an optical kill switch for the ignition. One more thing and I'll get off my soap box. Don't go too cheap on your throttle servo. The Owner's manual that comes with 3W motors makes a valid point regarding this. You want a good servo on the throttle for precise throttle control and quick throttle response. I can imagine where this would be a requirement if you want to fly 3D with the plane, because allot of the thing you do while flying 3D are very dependent on the throttle. If you want to set up your plane for 3D, you'll have to ask some of the 3D guru's on this site. They're all a great bunch of guys and they will be more than happy to help you out..
OK, my fingers are tired...................