I'm kinda a noob so I'm not too familiar with the more expensive kits but I'm currently just using a dinky dink scoche amp wiring kit (got it for convenience as it was right next to the amp) with my comps 12s and 900w amp and it hits about as hard as my friend's (we both have same setup except for wiring kit) and he has a memphis wiring kit. (Again I'm a noob so I'm not even sure it the kit determines how hard the subs hit). His subs do sound deeper than mine, can the wiring kit make a difference as to how deep the bass response is?
its more how much noise gets through to your speakers. With subs, you wont hear it that much but with mids and highs, you'll hear unwanted noise with unshielded flea market brand 4 channel kits.
You shouldn't notice a difference between a Scosche sub woofer kit and a Memphis sub woofer kit assuming they are the same gauge wire size.
If your using one subwoofer kit thats 8 gauge power and ground with 12 gauge wiring to the subs compared to a kit thats using 12 gauge power and ground with 18 gauge wire for your subs. Then you'll see a difference.
Subwoofer kits make more of a difference in higher power levels, lets say your running 2000+ watts rms and you have 2 choices. 1: those shietty soundquest 0 gauge kits from
amazon for dirt cheap. Its copper clad aluminum and its actually the size of 4 gauge wiring. 2: Sky high audio 0 gauge kits which are oxygen free copper AND they are true to size. You'll get more current to your amp with the sky high audio because 1, its bigger and true to size, 2, its made of pure copper which is a lot more conductive then aluminium/aluminum blend. So therefore with more current going to the amp, the amp will produce more power therefore making the system louder.
As for your friend's subs hitting deeper, its either 1: as pointed out by doesdad, different enclosures, different response in frequencies. 2: you might have the subs positioned in different spots which will affect the sound. Or 3: his vehicle's cabin gain is different then yours resulting in different sounding bass. Sub setups will sound different in each car.