Using Westone 3s with iPhone4 is the benefit from an amp/dac worth the investment?

Hello headfiers I am using a pair of westone 3s with my iphone 4 and am enjoying the sound, but I keep reading that people are getting a more dynamic sound with an amp added to the equation. I've also read some people that say it isn't worth the difference in sound. Sorry for the noob question, but I'm fairly new to this as I've only recently upgraded from sub $100 earphones to westone 3s. 

I don't find anything wrong with the sound unless I am using the largest comply tips then I notice muddied highs and upper mids, along with an increase in bass and the famous mid-bass hump that many people seem to notice with the w3s. But I'm just curious if adding an amp will change anything. For instance, add a bit more to the bottom end, or bring the mids a little more forward, or anything of the nature. 

Thanks for the reply kboe, I guess I won't really know until I take the plunge and try it out. 

After trying the w3s from my home amp and portable amp (e7) I got to say it is definitely better. The cymbals, kick drums, just about every instrument sounds more detailed and crisp. There is also an added warmth to vocals that make them sound more lush and enticing. It did take my ears a few days to get used to the new sound however, as at first I couldn't tell any difference. So overall, the extra purchase was definitely worth it.