Prepaid plans - need some advice!

Hey everybody! I'm in the market for a new phone, non-contract. Preferably of the smart phone nature (ditching my blackberry which I by NO means consider a smart phone. It's actually incredibly dumb). I would like to get on a pre-paid plan but there are so many these days and I am having trouble figuring out which ones meet my preference, as far as payment options. Any advice or suggestions on the matter would be much appreciated.

Here's the thing. I'm looking for something which I can, preferably, pay multiple months in advanced. I don't know if the type where you pay a bill for it would allow that. It seems like they wouldn't. That leaves the type where you buy a card each month, or every so many minutes or whatever. I don't have any experience here, but to me it seems that you should be able to buy, say, 5 months worth of cards at a time and just reload it each time you need to, to get you through for a while. The main reason for this is financial situations at the moment, which I won't get into. But I really need to be able to go ahead and pay in advanced now while I have extra money to spare for it. Just in case. I'm thinking Straight Talk might Work. I don't know if you can do this with Virgin or any of the others. So if anybody can clarify paying months in advanced for me, and suggest some brand worth checking out who allow this, please do tell!

Also, i care much about talk. My main need is text, a little bit of talk, but nothing extensive by any means, and data of course, since it's required for a smart phone anyway. Unlimited would be ideal, but given the ability to use wifi, a more limited amount could suffice, if it were still somewhat reasonable. Also, speaking about talk minutes, free nights and weekends would be awesome, especially with small number of minutes, just in case, but I don't know if that's even offered with many prepaids. Thanks, sorry that's so long. Any useful info, answers, or resources, again, much appreciated and I hope I'm not being overly picky. Just need something too destroy fit my situation.