its a hard question to answer though, as what u deem as sounding better is completely different to mine and to others.

U need to start as to what it is exactly u want from it. As just stating u want it to sound better isnt exactly helping.

Sound better in what way? U want more bass, u want more volume or u want it to sound clearer and cleaner.

A HU will help with most of that but will also depend on what u have to go with it. Just upgrading the HU will be a difference but will it be the difference your after?

IF u want more bass add a sub and a mono amp the amp would most likely need level inputs as not sure if the stock HU has RCA out or not. But in doing that it may over power the rest of the system.

If ur just after some cleaner sound i would say a new decent HU is a must, plus some new speakers to go with it with decent cabling.

Personally me, i would get a new HU have used alpine and have a older model 9815 HU that i paid alot more then the current top(so called) alpine model. A decent set of front splits running of a decent 2 ch amp and a sinlge sub running of a mono amp, you wouldnt need a massive monster amp either for the sub around the 200-500wrms would be enough and 75-150wrms for the fronts would be more then enough. I wouldnt worry about running any rear speakers id use the money to get better front speakers. Should be able to get all that for $1000-$2000 depending on the brand and level of gear u choose to go with. If u have some xtrra cash id sugest getting the doors with some sound deadening and diffusers for that xtra help with the SQ side of things.

Also recommend Marty at FHRX.

SSS_Hoon