In terms of quality, I couldn't really tell the difference. Theres a few videos on Youtube boasting about improved bass punch and clearer highs, but that makes no difference when I'm running half stock and half cheap two-way 5x8's. The big difference is the external amp reaches far higher sound levels than the inbuilt one before distorting.
If you ran your iPod you may noticed around 24-25 the amp in the unit becomes very unlinear, and runs out of headroom. I did intially complain to the company I bought the unit from saying this thing is ment to be x y and z, to which I was told in reality it puts out 18 watts RMS as standard, and that anything written on the facial is rubbish. As I thought I was popping the speakers but it was actually the unit itself.
This external amp however is much more powerful. I found the original speaker box for my 5x8 Alpines i have fitted in the front and they're only rated at 35 watts RMS, so I'm assuming the output figure is roughly right (45w RMS)
I still haven't got around to hooking my knackered speakers out (apologies Edge and Ian - I will get round to it sometime this week) but I really want to put some components in the front as that should make a massive difference in the sound quality as opposed to just the level.
I would say, if you're after a louder system and have speakers fitted which will handle the power, its a cheaper easy way to upgrade. I can see it's aimed at people like me, who like audio to be loud but can't be asked to go the whole haul and install amps and speaker wires etc. All you need to be sure of is that your current installed speakers are rated accordingly and that you have somewhere to put it, mine took all of about five mintues to fit.
I did intially thought I had a problem as I was getting a thunk (loud pop) everytime I shut the door. I hooked it all out Sunday to have a look make sure I wasn't being a dick and hadn't connected something properly. After deciding that I didn't like the look of the ISO to H/unit lead I hard wired it tested it and still had an issue. Only when I lent on the arm rest and found that caused the poping as well , and that the arm rest is all one with the facia where the radio sits and that if I smacked the side of the radio it did it to. Yes I win a Noob ICE Award, the plug wasn't properly connected in the back and it had gradually made it way out...
