Tacky after market? lol ...
You have a lot to learn ... the best thing I EVER DID, was run my 2 door speakers off an amplifier, the sound is second to none, and I can push the volume to 90% of full capacity without any distortion and until it makes my ears bleed literally!!
Do this, find out the size of your original door speakers, disconnect them, buy 2 x 3-way Coaxial components, the ones with a tweeter/mid-bass built in, run those 2 speakers to a tiny amp in your boot, and you'll see a MASSIVE difference. Then you can easily throw a subwoofer in their aswell for ridiculous sound quality.
Ive spent approx £400 on my whole setup, RRP. Not even used. RRP ... and its amazing. I got a 10" Sub, 4 Channel Amp and 2 Alpine (forgot the model number) door speakers. Aswell as a £70 Grundig headunit with 4 RCA Outputs, 2 for Sub, 2 For speakers.