I haven't got to test out a lot of phone/iem combinations with the RWAK yet. it's just starting to run in (about 200 hrs). Did a brief comparison on LCD X and AKG K3003 with RWAK240 and touch/Onkyo player/Hugo side by side:
Software:
Opus DSD Showcase #3 - various tracks
Scheherazade DSD rip - track 4 Festival in Bagdad
Michel Jonasz - La fabuleuse histoire de mister swing 1644 wav- Disc 2 track 2 Le temps passe
RWAK 240 balanced hp out > LCD X (2.5mm balanced modified stock cable)
Coherent and eurythmic, details in abundance, great instrument separation with an upfront presentation, excellent speed and attack.
Hugo > LCD X (6.3mm stock cable)
Different presentation than 240 - details are spread wider and deeper into the stage, instruments scale larger with a touch better body and decay than 240. Very musical but with speed and attack when called for.
With the LCD X, I favour the Hugo and agree that it's a match that is hard to beat.
With AKG K3003, the gap narrows up between the 2 units, both pairs really with it. The RWAK has a slightly more upfront, highly resolving and exciting signature ; whereas, Hugo is more relaxed and musical. My preference here will really depend on my mood and setting.
(Side note: Some early reviews just in from highly regarded sources in high-end audio trade praising the AK240/balanced Uber/Tralucent Ref. 1 pairing. I'll report back when i can get hold of a pair from spkrs01. I heard the stock is going really fast last time we met.)
IMO, whether you want to add a portable amp to the RWAK 240 will really depend on the phones you want to use, e.g. My ear cannot agree with TH900 straight out of the RWAK, but if you add a ASPT05/T06 in the chain the 900 will take a 180 turn. If you pick the right phones, adding an portable amp may only have a very marginal benefit. (Different story with higher quality desktop amp though)
I bought the RWAK mainly as standalone player and to try out as a source for the Hugo so I did't get the "s" version with true line out. For me, as an all in one player, RWAK 240 is the best I heard in the market right now with quality body to match.
Cheers.