Unless you get lucky and find used parts. That is, to get a 4 speaker system like mine - it really does have a lot more sound with speakers front & rear. However, you can get this system with 2 speakers and this amp for about $300. I have 4 Blaupunkt 75WRMS coaxial 4" speakers - which is what Rumble Road used to sell, for WAY too much money. Now RR is packaging something else I understand, as those speakers aren't made anymore. In any case, you also need to drive them with an amp. I used to have a Blupunkt 250 watt T-amp but TriPath Technologies who owns the patent went belly up and so no one makes class T amps any more. They were great because they had the fidelity of class AB amps and electrical efficiency of class D amps.
Anyway my T-amp puked recently so I was disappointed I couldn't find one anymore. So I surveyed what was available, wound up back at Blaupunkt with a class D 400 watt amp. I've been really surprised at it's audio quality, especially the highs I expected to distort, are quite good. And it has even more power - volume delivered without clipping or distortion - than the T-amp. That amp was $149 with free shipping online. If you got 4 speakers like mine you would pay around $300 for all of them. I also added Bass Blockers (large capacitors) to prevent bass from blowing the speakers - but a good amp, like the Blaupunkt ones I've used, has hi-pass settings, below which lower tones are blocked to protect your speakers. Read my article at
http://www.horseapple.com/Valkyrie/Tech_Tips/Jammin_with_Blaupunkt/jammin_with_blaupunkt.html Read about the amp at
http://www.crutchfield.com/p_023THA275P/Blaupunkt-THA275PnP.html?tp=115You can see 3 of the 4 speakers in this pic:

Here's the new amp:
