Scion T1805 HU to Factory amp 02 4Runner

[pjd]

Hi, Is it feasible to install a T1805 in my 02 4Runner keeping the factory amp and adding a Roadmaster RTS3000 speaker system? I have these items and just want to use them, specially the HU for the cd-changer and MP3 player. Also, what are the RMS values of the factory speakers and amp, and the T1805? Thanks in advance for your help.