I'd go 8x$6.5m for Necas, willing to bump to 8x$7m if he really presses for it. I think that's a fair deal for the term given where he currently is. Anything more than that, and he's just asking too much.
Given the volatility the league is currently under with COVID, it might make sense for these players to lock in long right now. Who knows what the financial situation will look like in a few years, so if you have the opportunity to lock someone up long term at a reasonable rate, do it.
Svech and Necas locked up through the 2020s at a total AAV around $14m is fair, and should give us plenty of room to still get the rest of our guys locked in as well.