Class D Amp

I'm getting ready to install Polk 501 front speakers for my supervalk, I've researched till kingdom come, I need advice, one of the favorite amps is a Rockford Fugate PBR 300X2, will this fit under my seat on top of the radio? Will I need to order anything extra such as cables, connectors, etc. Is their a new latest greatest amp that has come out lately? This last question might be tuff, but would be helpful, I want to get away from the IS radio and the death star pod, I'm not new age tech savvy, I'm looking for a radio receiver, it has to be small enough to either mount on the handle bar clamp or mounted on the handlebars....Thanks, Steve