Board Thread:News and Announcements/@comment-100.33.153.171-20140604230543/@comment-3153244-20140825113721

If you want to reach rounds 40+, you'll need both of those upgrades. I would also advise Spike Storm/Spiked Mines, Sabotage Supply Lines, Spectre and/or Ground Zero, at least Tier 3 Super Monkeys and MIB Village.

As for reaching rounds 30+, Ninjas, 4/2 Farms, Mauler spam and Tier 4 Spike Factories.

With the upgrades I mentioned above (and additional ones that I had for a little extra damage), I reached Round 50 (Tier 6 CT).