Have you considered switching to T-Mobile? Their new Simple plans are actually really nice and you can use GSM phones.
Check it out.
A 4 person family plan where everyone gets 500mb is $100 a month, with everyone getting 2.5gb of data it is only $140 a month, and with unlimited for everyone its $180. Not everyone has to be on the same plan either. So you can use unlimited data for yourself, then 500gb for everyone else and that will knock the monthly charge down to $120. Insane to get a 4 person family plan with data for only $120 a month.
The other interesting option is
Solavei. They use T-Mobile's network, offer unlimited everything for $50 a month per line, *and* offer a referral fee if you get 3 people to sign up. Basically, every 3 people you get to sign up gets you $20 a month. If you get 4 total lines, the total cost would be $180 for unlimited everything (same as T-Mobile's plan), but you have the chance to save more as you get more people to sign up.
For a phone, I'd go with the Nexus 4. Its not cutting-edge, brand spanking new, but it does have pretty up to date specs, plus its only $350 for the 16gb version if you buy from Google Play. There is no better value phone out there that delivers this kind of performance. Unless you really want a specific style phone, or actually like HTC's or Samsung's skin for Android, there is very little reason not to go with a Nexus 4 - unless you want to the expandable storage as others have mentioned. *EDIT* - Noticed you really want the SD slot. If you really can't live without it, you'll probably have to go with an S4. If you only occassionally need to access stuff on the SD card, you can use a $2 OTG cable from Amazon and use a USB thumb drive with your phone. Not practical if you need access to more than 16gb of space all the time, but decent if you occassionally like to swap out music/pictures. Unfortunately, most of the better (IMO) phone now don't allow for SD cards, so your choices are more limited. Nice thing about a GSM Nexus phone is you will get day 1 updates to the newest version of Android - Key Lime Pie anyone?
I'm recommending T-Mobile because I am in a similar boat to you, except I am really tired of Verizon and want to switch. I'm doing the math to see if it is worth it to end my current contract a year early and switch my 3 person family plan over to T-Mobile with Nexus 4s for everyone. With cancelling the contract and getting the new phones, it seems like it would just be a wash, so I may just wait until the contract is up.
Gaming: i5-3570k/Z77/212 Evo/Corsair 500R/16GB 1600 CL8/RX 480 8GB/840 250gb, EVO 500gb, SG 3tb/Tachyon 650w/Win10