stereo speakers to my pc

[elmadre]

i have a set of sony speakers from my now stuffed cd/tape/radio hifi set(sony FH-E6X midi hifi,the laser is stuffed on the cd player)- of which have the old red and black wire which have spring type clamps that hold the bear wire ends in both the speakers and the stereo systems amplifier. i bought 2(3.5mm) audio jacks and soldiered them to the speaker wires and plug them into my pc (i have a asus p5w dh delux motherboard with on board sound). when i set them both to line out in the realtek hd audio manager it gives me very little scale of volume-full blast is pretty low, but it does have a scale of volume. now any pc type 2.1ch. speakers are usually plugged into the pc and also a power socket and have their own volume control.
how can i use these speaker directly to my pc and get the kind of wattage as i use to with my stereo or do i have to use the amp (and how would i connect this amp to my pc).
i hate to throw away still working stuff.
thanks in advance!
elmadre