I've owned a V3, ACM HD-P2, and Oade MOD R4 (2-ch Warm, 2-ch Transparent). Can't speak to the Fostex at all. I thought they all sounded good, in their own way. If I had to rank purely on sonic quality, I'd rank V3 > ACM HD-P2 > MOD-R4. The ACM HD-P2 is a mighty fine sounding all-in-one, at a very reasonable price point. The MOD-R4 sounded quite good, and I loved the flexibility of the MOD-R4, with the option to run Warm or Transparent, strictly 2-ch, or 4-ch (4 mics, or 2-ch mics + 2-ch SBD). Tough call. Do you find yourself wanting to do 4-ch, or are you more interested in 2-ch?
Keep in mind if you go V3, you still have the additional cost of a recorder / bit-bucket.