Your specs aren't too far off of mine. With the parameters you laid out if I went out and bought a new 3-ball arsenal, these are the options I would consider:

Heavy - Grudge. A good combination of a cover that digs into heavy oil and and an overall effect of retaining energy down the lane.

Medium - Gamebreaker MVP. This is a really nice benchmark ball that's also versatile. If it's a bit too strong then adding some polish should out it right where it needs to be for this 3-ball arsenal.

Light - Joy Ride. I've seen a bunch of people use these in my area and they all look good. There are a lot of new releases coming up this summer for light oil balls but I would feel comfortable with the Joy Ride regardless. It's a great ball.

Get a Hammer Scandal for heavy oil.
Because it's seriously the best ball out there at the moment. It has the most hook out of all the balls out there. Only ball that can compete with it is apparently DV8 Grudge.
And besides, nothing hits like a hammer. Which is very true, there's something special about the Hammer balls' punch. I often get some odd strikes, that wouldn't be a strike with the other balls I've tried.
Don't ditch it because it's not an asymmetric ball. It's just bs that symetric balls can't hook more than asym balls.
Hammer proves to people who spout that bullshit with the Scandal.
And the ball has a 3 year warranty, which is the best warranty on the market.
Storm has a only 1 year warranty on their balls, and others have 2 years. Most of Hammer's balls have 3 now.

I'm gonna try not to dis other companies, but I wouldn't buy a Storm or Roto Grip.
The only ball out of their new released that I've read mostly good reviews about is the Alpha Crux.
I'm very sure the Scandal is better though.

I'm hooked(pun intented) on Hammer atm.
So for medium oil:
Arson High Flare Solid or Arson High Flare (because it looks cooler xD)
Light oil:
The new Viral Hybrid

Don't bother getting a polyester spare ball. If you were thinking about it. Unless you can throw the balls straight towards the left over pins.
I couldn't, so now I'm using my Scandal for sparing too.
I'll probably get a second Scandal for the next season, and use the old one on the alley where the lanes are shit, and the new one for the lanes where they oil it before every match and every practice.
And one lower performance ball, incase the lane dries up a lot. I'll probably get the Arson High Flare, unless something new and great comes from them.

If you went 900G, I'd wait for some of the new releases. Inception (heavy), Respect Pearl or Drift for mild symmetric (Respect has a stronger cover/core combo), and a Boost to round it off.

I have similar specs.  I dunno which of the bottom two categories it would fit for you, but I love love love the black/gold spike.  Mine sometimes skids a little too much on fresh medium, but it's borderline. Sometimes I can use it starting first game, sometimes I have to wait until second game.  But great ball and I believe you can still get it.

I would go:

Nirvana or Grudge for heavy oil
Ridiculous Asym or Zone for Medium
rack attack solid or Rhino for dry

With your specs 16.5 mph and 300 rpm, puts you in the "slightly rev Dominate" category or your ball speed and rev rate match perfectly. It depends on how you get your specs.

1. Ball speed should be measured at release.

2. Rev Rate needs to done with a camera and tape on the ball going from PAP to above the fingers.

3. When you have the PAP you can determine Axis Tilt and Axis Rotation.

 
I would make sure specs are good before buying an arsenal.

As TKKshop has stated the Venom Shock.  The best medium ball currently on the market.