Hi I got the top of the line Diamond Audio speakers hooked up to a JL 300/2 amp running off of the stock headunit and the sound hurts my ears would a new headunit alleviate this. Its just too sharp

 

You can upgrade the stock audio but you may find as you did there is always a weak component if you upgrade far enough.

If your speakers are very high end and you give them very clean power then your headunit will send you loud and clear music limited to your CD recording (or other music source) or your headunit's ability to send a strong and clean signal to the speakers.

I replaced my speakers only and didn't really hear that much difference from my stock headunit/amp.

I added a four channel amp and that helped but then I could hear how bad my CDs were. Even good CDs didn't sound as clear and clean as some aftermarket headunits.

I added a Nakamichi CD400 player and that helped alot but I can still hear bad CD recordings very easily.

So- get some known really good CD recordings that you are familiar with. I like the hybrid SACD/CD recordings. Play it in your MINI and also in a audio shop showroom with the headunit you'd like to add. Listen for a big difference.

I find that burnt CDs and MP3 CDs are not very good music sources so be careful how loud you play them.

 

Speaker level inputs are always a compromise, especially with a stock head unit. Most OEM headunit amps are bandwidth limited (50Hz-15kHz) because it it's more difficult to produce the extremes of the audible range. Also, the amp is usually rated at 10% THD+noise, instead of the typical 1%. This is one instance where the gain in the JL amp is better then the source. Turn up the amp gain and turn down the head unit to ensure the head isn't trying too hard.

Since the 300/2 does not have speaker-level inputs, you must be using some convertor. It's very important that the grounds are all at the same potential. If there is a difference, you will get some awful high-frequency noices. Make certain the convertor is installed according to the directions. (Often, the case of the convertor is the ground and needs to be securely screwed to metal, near the amp.)

A headunit with line-level outputs will be much better than your current set-up.