I am wanting to put a custom stereo and some subs in my car. What head unit fits good? and what size subs will fit good in the trunk and still have storage space?

 

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Go to crutchfield and get some ideas. They are expensive but you can at least see what models fit and then go from there. They have a sizing guide and will tell you which ones require modifications and which ones dont. As for the sub, You could do a few different things but my ideal setup would be just a component set in front and then a good sub in the back. I'd like a 10''-12'' for a great sound quality with a good amplifier. I dunno if a 12'' would fit though. I usually buy all polk audio. Great quality, great sound.
GL man, also, if you can, get a good head unit with timing allignment.