Hondas stereo's all use 4-ohm. You can prob bet the RMS rating of the stock fit is around 15-20 watts a channel for 4 speaker base/LX and 10 watts x2 for tweeters and 15 to 20 watts RMS x4 for the full range drivers in the doors for 6spkr system.

 

I have two sets of infinity kappa's coax installed in my car for 1 month before I decided to go crazy and upgraded to all Audison Voce speakers and amp. The infinity sounded great for what they cost. I will be posted mine for sell for $100 both sets.
Infinity Kappa 62.9I 6.5" Kappa Series Car Speakers

 

Have you found a subwoofer yet? I got this:Walmart: Kicker PT250 10" Subwoofer with Built-In 100W Amplifier

from Craigslist for $100 new( pretty sure it was stolen) and you don't need power amp for it. Unless you're an extreme bass head, this is more than enough and very compact.
The bass is actually overwhelming at just half the intensity so I keep mine toggled at 3 out of 11.

 

YOur objective is too add bass to the OEM system. Mine was a bit different. Wanted to keep the OEM head unit but improve its all-around performance. Therefore I got a sound processor which has f & r speaker outputs, plus a dedicated sub-woofer output (all RCA).

For your situation, you'll have to tap the speaker wires from the L & R speaker (front or rear, not both) and hook them to the powered sub's inputs. Best to use the door speaker wires rather than tapping the OEM HU harness. Not the tidiest way, but certainly the quickest and simplest.

Why do it yourself?? You learn lots about the Fit. How things come apart and if anything ever goes wrong, you can trouble-shoot immediately instead of paying a shop $ for labor. Have literally taken my interior apart and it took almost a month to do all my installs but the learning curve jumped dramatically.

Was it worth it? For what I wanted - a quieter sub-compact, plus audiophile-like sounds - definitely yes!!!! At 80mph, virtually no wind noise, crystal clear sound, firm solid bass, zero distortion.

Good luck. Take your time, research more, analyze your options carefully and you'll end up with the results your after.

Don't forget, when you start the install, as with anything electrical in a vehicle, unhook the negative battery terminal before touching any of those wires.

 

are there any unused grommets or easy feed-through points on the firewall to run the power cable to the amp? In the past I've poked a hole in the main wire boot, following a "tutorial" online. But on a brand new car I, personally, can't drill into the metal. What did you do?

 

I too am interested in adding just a sub to the Fit to even out the weak 1/3 of the sound system. The trick is where to tap into the speaker wires?

 

I am planning to tap into the speaker wires at the doors too, I can't bring myself to cut a new loom and there seems to be enough space in the door grommets.

I will be making a fibreglass and mdf box to house a slim mount 10 inch sub and building it so that it is tucked into the right rear corner and not over hanging the spare wheel cover. When I have the cash, I might buy one of those small amps and hide it up behind the glove box as on the right hand drive cars atleast, there is enough space up there but for now I will be recycling a very old MTX amp and attaching it to one of the back seat support frames so that it is out of the way both when the seats are down and when they are folded up.

 

I just spliced into the rear door wires yesterday. I used 14 or 16 gauge stranded speaker wire, and it fits all right. I had to use a fish wire in order to get the wire through the boot, but it worked fine. I just soldered the additional wires to the tabs on each speaker.

 

Nice post!!!, just as information, there are some adapters mount for HONDA speaker and wires too

Honda-Acura Speaker Mount Plates Adapters


Honda-Acura wire concectors Metra 72-7800


More details in this post

Hope this information helps you...

Luis
Honda Fit Sport 2013 - Vortex Blue Pearl