audio question

I've always heard it sounds better with an aftermarket headunit rather than an OEM headunit.

My V never had an OEM headunit so I thought about getting one but everyone says aftermarket is better than OEM(in this case).

I replaced my radio but left the oem speakers and I think it sounds just as good I want to replace them one day but for now there fine

It really depends on the type of Aftermarket Head Unit you buy. If you buy a cheap one, then it will probably sound worse than the factory HU. With HU's and any audio equipment YOU GET WHAT YOU PAY FOR. Go with something that has a good graphic equalizer and a wide range of audio settings. A good quality HU with a in 7-10 band equalizer built in is that way to go.
Good Head Unit with good audio settings could mean the difference between buying new speakers or not. Meaning, if you buy a cheap HU then you will probably have to buy new speakers to compensate for the poor audio settings.
If you go with someting decent then you could adjust the sound to where the factory speakers sound just as good as aftermarket ones.