The absolute best solution would be digital all the way - which you could achieve with a cheap soundcard or USB device for the PC with S/PDIF (aka digital, optical, TOSlink) out, and a Digidesign Audiomedia I or II Nubus card in the 650. They're reasonably cheap if you get one on the right phase of the ebay moon. It's coax S/PDIF only, so you need a PC card with coax out too, or a converter (not cheap or make your own)
Barring that, either machine will do line level analogue recording, and either will have enough grunt to record two channels (ie stereo) at 16 bits and 44kHz (CD quality). "Omni" means that it can record at line or mic level (mic is a lot quieter) and there should be a control panel to adjust the input gain.
If you can meter the inputs visually to check for gain and clipping, that would be good. I don't recall if you can do that from the control panel, but you can do it within most audio programs (Sound Designer, Deck II for example). You want minimum gain on the 650 and the signal from the PC should be near the top, but not clipping, on the Mac, when you play the file.
Beyond that, it's just a question of disk space.
Oh, I'm not entirely sure if the AM-I has S/PDIF, but I know the II does - I have one. And there's a PCI version, so make sure you're getting a Nubus one.
Barring that, either machine will do line level analogue recording, and either will have enough grunt to record two channels (ie stereo) at 16 bits and 44kHz (CD quality). "Omni" means that it can record at line or mic level (mic is a lot quieter) and there should be a control panel to adjust the input gain.
If you can meter the inputs visually to check for gain and clipping, that would be good. I don't recall if you can do that from the control panel, but you can do it within most audio programs (Sound Designer, Deck II for example). You want minimum gain on the 650 and the signal from the PC should be near the top, but not clipping, on the Mac, when you play the file.
Beyond that, it's just a question of disk space.
Oh, I'm not entirely sure if the AM-I has S/PDIF, but I know the II does - I have one. And there's a PCI version, so make sure you're getting a Nubus one.