Hey Hogan, there are a couple of options. If you are going to keep the RapidStrike stock wiring, the best replacements are MTB Honey Badgers ($4.75 ea). They're pretty much drop in replacements, but you might want to consider upgrading the rev switch, especially if you use IMRs.
There are also Meishel 2.0s ($3.50 ea). These drop ins are good solid 130s with slightly less power, and no need for switch upgrades or electrical mods other than removing the thermistors.
Another option is Pololu Solarbotics RM2s ($2.25 ea). They are also drop in replacements, but with less torque and a slightly longer spin-up time. You can literally solder these in with no other mods necessary.
If you're going to use the stock flywheels, then keep the stock cage. If you're upgrading the flywheels, and you're looking for good performance, these new Worker aluminium oblique flywheels are exceptional. They're a metal version of the classic plastic rifled flywheel. They grab onto the darts really nicely, but they tend to beat up the foam a little. You'll need those Honey Badgers to drive them.
The jury's still out on concave flywheels. Some concavity is clearly a good thing, But the issue with highly concave wheels is the difference between the rotational speed of the deepest point of the groove (the inversion point), versus the speed at the outside edges. Most of the surface area of the dart is in contact with the slowest part of the flywheel, so the outside edges are really just chafing along the sides of the dart and not really helping.
There are more than two dozen different flywheel choices these days. At low power, they all perform similarly. It isn't until you get into high performance blasters that you start to notice any substantial difference. I have tried many, and been pleased with all of them. I tend to like metal because the material is thinner and lighter, buy hey, that's just me.
Unless you're planning to go 2S or 3S with good motors, you're not going to have enough torque to use a high crush cage, or anything too nonstandard. So I suppose you could print your own cage, similar to this BlackSteelProps Proto Stryfe. If you want a really nice one, the Worker aluminium cage is a thing of beauty.