OK - nice cans. I guess the question is - are YOU happy with your current set-up (ie the sound quality)? Don't necessarily go by a few comments you hear. I was very much anti-Apple (read big Cowon fan) before I actually got to compare the two side by side.
If you're looking for tweakability - get the Equalizer app - it's a no brainer for a few dollars. I love my Shure SE425's - but would like them to have slightly better highs (their mids are perfect). With a decent EQ - no problems
If you want to take it another step - you could try an entry level amp. I own the E11 - and I find it a very nice pairing with my Touch and current IEM's / cans. It's quite a warm amp - but that suits me. The good thing is that it has a small footprint, and has some real oomph - so should be able to drive cans needing a little more power (future purchases). I haven't tried a CMOY - but the JDS gets very good reviews. I can't comment on the pav2. Personally I wouldn't get the E5 - especially when the E11 offers a lot more, but doesn't cost a great deal more.
The other advantages of using an amp are being able to use the LOD on the Touch (better signal), and also I think the SQ is better (for me). I don't notice a lot of impact with my IEM's - but I do on my SRH840's.
The cons of using an amp - pretty much cost & also having to carry something else around. Basically I use mine most of the time - except when I'm running - then I just use the iPod and my IEM's.
Don't expect night and day improvement with an entry level amp. For me - about a 5% increase in SQ - but that justified my investment.
THE ALTERNATIVE
If you're simply looking for a change - don't worry about an amp for now, and consider a second pair of cans, or maybe IEM's. Maybe look at getting something totally different. The more you try, the more you tie down your ideal sound signature. Plus it's fun being able to compare.
Not sure if all this helps or not. Just don't get caught up in all the hype. And take any advice you receive with a grain of salt (even mine). We can only give our views - we can't translate them into what you will want.
One last bit of advice - be very aware of posters who say "get the [insert cans here]" with no reasons why. Often they are quoting what they have in their inventory with very little thought for what the poster is actually asking for. There are a few that do this a lot on head-fi at the moment.
