Focusrite/Apogee Interface Delay Compensation

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Hi,

Few questions for anyone using the Focusrite RED (4pre/16L) or the Apogee Symphony MKII regarding delay compensation.

I'm running PT Ultimate software, it'll probably be with a TB Native box in a post production, 5.1 environment.

Regarding the Focusrite interfaces, they look great for I/o expandability vs something like the Omni but I've read that the converter latency does not match that of a Avid HD i/o unit so its a few samples off. If I'm working in the box (no hardware inserts etc), mixing or sound editing, does that extra latency only effect me on the D/A conversion on my outputs to the 5.1 speakers?

On the flipside, the Apogee is a sample accurate conversion but is a lot more expensive but if its clocks better, it might be the better option.

Lastly, I'm also thinking it might be worth skipping the HD Native box and going straight TB and Ultimate software - any thoughts?
Thanks