Do most people use an amp for thier mids?

or just for the subwoofers?

It really depends how much power your mids need. I only have an amp running my sub and let the head unit run the stock mids in the doors as they're loud enough for what I want. If you're trying to run 6 x 9's or sumthing similarly power hungry your head unit will struggle to give them a clean, powerful signal and you will need an additional amp or a powerful multi channel amp.

I have dedicated amps for my single 12" sub (2kW+), my mid-bass (370 wpc), my mids (120 wpc), AND my tweeters (85 wpc). Granted, I am fanatical, and generally speaking, overkill is a good place to start for me, but sure, there's no reason in the world (other than complexity, expense, damage dealing capability, charging system requirements... etc., etc. ) to not bi- or tri- amp your system (or, in my case quad-amp). Pretty much any amplifier will provide a MUCH cleaner output signal to a speaker system than would any head unit. There are a few exceptions to this rule, (both ways) but very few.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

While you don't need to get as extreme as haemphyst, I would never run aftermarket mid/high speakers without amping them. :-) Bi-amping is sufficient for most folks. ;-) New Project: 2003 Pathfinder