Can I use home audio speakers in car?

Well, you can, but the impedence (ohm rating) of the speakers should match that of the receiver. Here you will have a mismatch of 4 & 8 ohms, which means your home speakers will be only about half as powerful running off the 4 ohm source since the speakers are impeding at twice that rate. You can use 2 ohm speakers in your car if you have any of those, since the speaker ohm rating should be equal to or less than the recweiver rating. If you add up the number of channels your receiver outputs and multiply the ohm rating by that number, you will get the maximum ohms you can run with optimal performance output ( wattage). I assume you have a 4 channel 50 watt receiver (200 watts max output, so that means 16 ohms total. You are talking about putting 32 ohms onto those 4 channels, which will probabaly cut your wattage in half as the speakers "impede" or cancel out half the input from the receiver. The ohm ratings are different because home speakers/receivers run off A/C current, and car systems run off D/C current. Unless your receiver has more than 4 channels, any surround speakers will only split an existing signal and will not provide the signal-splitting you are used to at home. I would recommend getting 4 ohm speakers for the 4-way setup, or 2 ohm speakers for a 6-way setup. You can direct wire speakers w/o installing first to see what happens.