I just installed a JVC KD-NX5000 into my 2008 Sonata (Replacing a V480s OEM stereo) and seem to notice that the power isn't what it used to be.

the JVC website lists these as the power specs for the KD-NX5000:
Maximum Power Output 50W x 4
Continuous Power Output (RMS) 20W RMS x 4CH at 4 ohms no more than 1.0%

The Hyundai service website lists these power specs for the factory headunit:
Max 20W x 4

That means that my JVC is more powerful than the factory stereo, right?

If so, I wonder why it sounds wimpier.. Should I fiddle with the EQ more, or buy a 40x4 RMS amp?

Will buying an amp give me any benefits since it won't be more powerful than my headunit?

Car Audio newbie here - please be nice. :)

I use to work for a BIG electronics company that everyone in the US sees their name on tv. But anyways, I worked in Car Audio and to answer your question. NO, you don't need an amp. if you amp your factor speakers, well just be prepared to buy new ones. If probably sounds like crap because you haven't set your EQ. Some head units have preset EQ's, while others you can set your frequencies on your highs and lows (some have it for mids). But look at your manual for the new head unit and see if you can change your frequencies. Hope this works for you.

PS
Nice head unit

Amps are what you need. If you are running subwoofers you definitly need a 2 channel amp of atleast 400watts. For speakers you can get a 4 channel amp. To my subs im running a 1600watt amp but my battery can bearly handel it. But yeah the head unit can only pump out so much and an amps purpose is to boost the signal.

You should be able to adjust the eq.Make sure you don't have any wires backward(+ to -) this will cause low volume.Some head units are body grounded ,others need an additional ground.
As far as amps go the factory speakers wont take much over factory amperage for extended times.
I have a 150watt rms 300 watt max Kicker KX150.2 on a 150 rms 300max Rockford Fosgate phase 1 Punch 12 inch sub and sound is plenty with all else stock,including head unit.

Im kinda late to the thread, but I just bought the car this week.

Anyone checked the factory speakers with a meter to see if they are, indeed 4 ohm impedence?
If theyre 8 ohm, that would explain lower output with replacement HU

im late also but before adding an amp get rid of the crap
stock speakers