car speakers.

[globalplayer-svk]

Ok, i hope someone here can give me answer that satisfy me:))

so i have car, older car, and i have there sony xploid,(radio with cd/mp3) which has 4x50 w .
in front doors are original speakers, connected on 2 slots.
i will mount also 2 speakers on rear (under rear window)
i am looking on

http://www.magnat.sk/car/racer_320.htm

and my questions are:
will it play? i mean will the radio have enough power for the two speakers?
or i need amplifier? and when yes, how strong.

(sorry if someone think that this is dumb question, but i will have this car maybe 1 year so i will not invest too much moneys to it.)

thank for any help and answers:)

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