Which should I get to add to the collection?

Hello all, it's my first post here, though I've been a long-time lurker.  I've also been a forum member (though not very active) at Audioholics for years.  

First a bit about my setup and my tastes:

My "primary" audio setup is a huge FLAC (and a small SACD collection) library fed to an EMU0404 USB DAC, and from there fed either to a plain old Denon AVR to JBL Studio L speakers (not high-end, but very nice for the money), or to a Headroom Micro Amp (Desktop configuration) and out to Sennheiser HD650's w/ Cardas cable.As lovely as that setup is (I sometimes do tire of the 650's "veil" though), I find myself using it less and less.  Being tethered to the desk doesn't seem as desirable since more portable solutions have caught up so close to high-mid-range gear.

So my current "mostly used" setup is an iPod Touch w/ FiiO LOD + E11 amp.  I just got the amp recently and bo do I wish I'd added it sooner....it does wonders for my IEMs!  I play mostly 256kb/s MP3s & AAC/M4A's both from Amazon/iTunes, and my own Lame & Nero AAC transcodings of my huge FLAC library.  I hope to shortly add a small one drive Synology NAS to run as a transport via DLNA in MLPlayer or Synology's own player software so I can stream an ALAC transcoding of my FLAC library instead.

My tastes in music are pretty broad.  Classical, Jazz, Bluegrass, Celtic, some Electronica/Chill, some pop-electronic, and some other stuff that can't really be classified in any category.  

Which brings me to my current IEM setup.  I have a few IEMs:

UE Metro-Fi: Awful....oh how awful.  I got it for a specific "need a cheap phone I don't care about" purpose.)
UE SF 5 (non-'pro'): Mostly retired and diminished to "on the go, pocket use".
UE TF10: Fantastic once amped and once Sony Hybrids are in use.  The sound signature is unique, and that's both good and bad.  It excells for most jazz, excells with solo instruments (baroque chamber music, sonatas, even quartets), does great with a good amount of bluegrass and celtic where the bright instruments are the focal point.  Dread-awful for electronic, and orchestral and most vocal centric things (opera, vocal dominant bluegrass/celtic etc.)
Klipsch X10: New addition, I like what they do for some things (opera, electronic.  SOME chill)  But they seem too "bloated" for a lot of other things.  They remind me at times of my JBL Studios.  I'm not sure if that's good or bad.  My big problem with them is with a wire like that they'll be broken pretty fast no doubt.
HeadDirect RE0: I "like these", I know they've been compared to Ety ER4's....but they seem too flat and analytical to be interesting.  They remind me of the HD650's but without most of the great attributes of the 650's.  
And of course the 650's themselves.  Power guzzlers that they are...but amped they can do great things.

Now, my question is this: If I were to add something to either "upgrade" the existing, or to "fill in an area I'm missing", would that be best served by SURE SE535's, Westone 4's, or some other option I hadn't considered yet?  Or would I be better off adding another set of full cans like AKG702's or something to the mix?

I like the idea of replaceable cables which would rule the Westone's out...though I've heard of a handful of jack issues on the Sures, so it may not matter as much after all.  One thing that I like about both of those is I believe Olives will fit on both.   I loved the olives when I tried them on RE0, but the poor connection to the nozzle due to "olive mod" attempts turned me off from them and back to the relatively poorly isolating Hybrids.

Anyway, I look forward to hearing suggestions (including those saying that "if you have amped TF10's and X10s, why are you looking for upgrades?" :)
 

Thanks for the reply!  Fair enough, and I half suspected that regarding the 650's.  They were a good value years ago when I bought them and it appears they still are a good value.  I'd love 800's, but not at that price point.  Though it's still a much better value than those crazy Orpheus were....

How about on the IEM front? Any upgrades/gaps I have with the TF10/X10/RE0 lineup that could be solved by 535's, W4's or something else?