For the 507 (and flagship 588) Meridian ditched their established whole-mechanism-slides-out-type transport in favour of an outsourced cd-rom drive. While their reasoning was logical - the player could read ahead, and even re-read, on-the-fly - it marked a build-quality change that existing customers found hard to swallow. I haven't heard a 507, but I understand that the earlier 506 and 508 models are held in higher regard, despite the 507's market value. I've also read that the cd-rom drive in the 507 is noisy, or at least louder then the whisper-quiet transport in the older players. I have a 506.20 and I love it. While I might be tempted to upgrade to a 508.24, the 507 holds little appeal. And if your considering a 506 I'd recommend auditioning the 20-bit player as well as the 24. I understand that the later 24-bit model gained extra resolution (understandably) and a more analytical sound, but lost out to the 20-bit in terms of pure musicality. I'd certainly like to try the two side-by-side.