Need help with internet.

I sometimes lag. Actually, I lag a LOT. I checked my info and found that my modem is 56k. I'm guessing this means it can stream up to 56k per second or something.(I can only go up to 60kb per second whilst d/ling)Can anyone recommend me a modem?I can go up to a $250 pricetag. Or is something else the problem?(Dlink DI-524 High speed router here) I'm really not computer-savvy, thanks in advance. xD