You'd better read the FAQ-section, then you should know if you need an external amp or not. (If the factory installed radio has a line in (eg. for a CD-unit) then you can use it as an amplifier with all advantages/disadvantages discussed already)

The type and brand of amp doesn't depend on the unit that gives the input but should somehow fit to the speakers. (Watch out for good speakers - they are the most important thing for sound quality - as you can read somewhere else in this BBS)

The only thing you will need is some money..

TeeMcBee