From what I just read, it seems like would need the $65 Smartphone Monthly Plan With Data (1 GB). Both phones that you mention are Smartphones. But, maybe you may be able to use the $25 plan but it says "Smartphones users must purchase a data package to use data services on this plan." Not sure how much a data plan would cost you. So it seems you can use a smaller monthly plan.
The $50 Monthly Unlimited Plan is for Quick Messaging or Basic phones.
With my personal phone, I used the $25/mo plan just fine for a couple years with my SGS2. The $25/mo comes with no data however, so if cellular data is necessary to your day-to-day, then you'll have to hand out more cash. Personally, I'd recommend doing what I did and jump over to StraightTalk. Muuuuch better deals that AT&Ts GoPhone services, and you can still use your carrier locked AT&T phones.
Thank you for the help! My boyfriend just got the phone, and I put my sim card into it and it works with just the texting. However, if you buy the phone and use the sim card that came with it, you have to spend at least $25 a month unless you call customer service and ask them to change your plan.