I reviewed the EX1 with comparisons to the GR07, RE400 and CKR9... it's in my sig.
Basically EX1 has good quality bass but less quantity and might lack slam and impact if you're going for the IM70. GR07 to me has the best tuning, just enough quantity and quality.
Mids is not EX1's strength... it's slightly recessed. IM70 (basically a CKR9 with worse treble) and GR07 easily wins this one.
Treble is airy and extended. Much further than the IM70, just as far as the GR07 but less harsh. It's my favorite treble.
Soundstage EX1 wins easily. Width, depth, imaging... top-notch. GR07 is mainly width with nearly no depth.
It's very good value for money, but if it's bass and beautiful mids you want you won't get it.
i just ordered IM70. I am using a cowon C2 and really loves its sound with 20$ ath ck505m. It is the sound quality of this cheap AT(i am not using 60$ XB90EX for the last 5 months) which tempted me to buy IM70. I am also looking to upgrade my C2 and can anybody suggest a Hi res budget DAP which sounds similar to my cowon and compliment IM70. My music files consists of mostly 16/44 flacs. And sorry for the bad english.