The assumption right now is Horvat is going to cost a 1st PLUS a guy like Wahlstrom. He's getting a 1st, minimum. After that it comes down to how many teams are bidding.
Then you want Kuzmenko, who by all accounts is someone they want to build around - to the point where they would trade Boeser to keep him. If it becomes clear they can't though, you're probably looking at another 1st or something of similar value.
Beyond that is the cap, which I'll admit I have no idea how that would work at the deadline, but I'm guessing we'll have to send back more than Wahlstrom's 900K. So yeah, you're probably looking at another 2 1st rounders or similar value. That's what Vancouver can most likely get if they trade them separately.