Size of speakers and amp recomendation for JVC KW-AVX800

you need to find out what size speakers you have now and upgrade them with that size the amp you get will be based on the rms rating of the speaker. Example if the speakers rms rating is 100 watts the get a amp that puts out between 100 and 120 watts rms also to add bass you could go with a subwoofer that will add all your low freq. If you want something that doesn't take up alot of room try a bass tube you can get one amplifed or not.

Good Luck