I've used 2Ks, 5Ks, 10Ks, and even 18Ks in different projects in different locations for different effects.
I've had a 10k fresnel with CTB, a silk and shooting through a window metering at f/2.8. I've had the same 10k shooting hard at a wall I wanted to blow out metering at f/22.
The answer to the 'best' lighting kit is: What is the film, and what are it's lighting needs.
The other thing you have to think about is: How the hell are you going to power these things? You want a 5K for something? Cool, how you going to run power to it if you're not on a soundstage with 3-phase power? You going to buy/rent a big enough generator, and a Gaffer who knows how to run distro long enough so that you can get sound?
I'd probably go with the second option for it's versatility, along with scrims, silks, barn doors, diffusion and a collection of gels. But keep in mind that if you plug a 2k into your home circuit, you better not have anything on that circuit drawing power or you'll blow it.
It's somewhat of a catch 22 when balancing to daylight - CTB has a transmission factor of 0.3, so if you use a 2k with a CTB, you're losing 70% of your light, but you also can't use any other lights on that circuit to push up the level. That's why HMIs are so popular.