will a standard kenwood headunit be able to power 4 6.5in 30 rms speakers or would i need an amp for those?

 

It will make sound, but the head unit gonna be like screaming to put power to those speaker while with amp, it's just gonna talk to them, so always better with amp, clearer sound.

 

most aftermarket decks make around 18-22rms...you will be fine if you just want to upgrade sound a bit. Tune the deck the right way...don't over eq it, I'm sure you don't drive around with volume maxed out everywhere every minute...it will sound fine, the deck will not be "hurting" to put power to them as stated above. An amp is always recommended though. In the meantime just don't try to make system do something it can't or shouldn't and you will be fine.

 

Ditto the above^^^ the HU will have no problem driving the speakers, a 4x30-50W RMS amp would be better but only because it would allow for cleaner/higher SPL levels, the saying is "it is better to be over-powered then it is to be underpowered"

The limiting factor for the aftermarket HUs "performance" is power supply, the stock 12V+ constant power, [memory power lead] can not supply the currant the aftermarket HU requiers for max RMS output, the 12V+ constant is just for memory power for the stock HU, but the 12V+ constant, [yellow] on the aftermarket HU is it's main power.

You can improve the HUs capabilities by supplying it with more power, [current] instead of using the stock radio harness 12V+ constant power lead, run a fused 12ga power lead, [up to a 40A fuse] from the batt. to behind the HU, [like you would to an off-board amp] and connect the HUs 12V+ constant, [yellow] to it, don't forget to cap of the stock 12V+ constant so it can not short out.

You will also need to run a 12ga "grounding strap" from the chassis of the HU to the cars chassis.

The above ground strap may or may not be needed, depending on MM&Y of car and how the HU is mounted. 94

 

^word.

 

+1. I didn't want an amp for the fronts either and wired the HU directly to the battery with heavy gauge wire. There is an audible improvement in SQ. This is not something subtle that you have to contemplate or use instruments to detect. Can now crank HU to 85% volume before noticeable distortion (on stock 12V from harness, distortion is audible around the half-way mark).