Here is the situation: 21 days left on my Norton A-V. I have had it for I believe three years now. I always get three PCs and let my family share. Now my ISP has always provided Trend Micro - Titanium for free. Newegg has 3 PCs Kaspersky Internet Security free after rebate. I never get a bleep out of Norton and also own (for life) and am monitored by Malwarebytes Premium. Thank you for your opinion, a confused ratchet!
Trend Micro has good web filtering while Kaspersky has good behaviour blocker I believe (although tests may conflict). Whichever you choose, I would select the more convenient option.
I'd upgrade to Norton 2015 if you like Norton, it has some remarkable improvements in 2015. But if your ISP provides Trend, and that includes Trend 2015, I would use that in a second as it's free, and 2015 is VERY good. My ISP provides F-Secure Lifetime for free, and I don't use it as I do not like F-Secure, I wish they'd change to Trend or Norton!
If I understand you correctly, and you get Trend free, and you have MBAM on top of that, you are in good shape -- at no cost. Trend became really good recently.
Regardless of the direction you choose, there is no harm in giving trend a trial run. Your ISP is providing it for free. It's very good. Kaspersky is also a great product. Not a big fan of norton, but it is also a quality product.