New Router/Modem?

[TheBiggmann]

Currently I am using a Siemens Gigeset SE567 that was provided by my isp, but I think it's getting kinda overloaded and doesn't have the power to broadcast across my house that I'd like. I have a 3 story log home and when you get down to the basement the signal is really weak. The landline is hooked up to my desktop and it intermittently powers 3 laptops and a PS3 when we are any combination of them at a time. I think this only offers wireless g and i would like to upgrade to an n, as i hear it is considerably better, especially when it comes to broadcast length. Should I just get a new router or will it be more effective if I get a new modem and router? If so, are there any suggestions for a reasonably priced combination or single router?