Audio Interfaces And Real-time Processing, advice and clarifications needed... Options

[axou]

Hi all !

I currently own a Roland SC-D70, which basically is a USB MIDI sound module, that also hosts a mic/guitar input. To achieve real time audio processing (mainly on guitar signals), I plug the output of the module to my Tibook, and apply effects on the Input 1-2 object in Logic. The processed sound comes out of the Tibook. The sound module comes with ASIO drivers, but unfortunately they're not really good, and I have to use SoundManager for the processing stuff.

Anyway, I'm now looking for a better audio interface that could handle multiple inputs, all processed separately using VST effects on Logic, with separate outputs as well. What I don't really understand (being a newbie and all) is : when using ASIO drivers and applying effects on the interface inputs, does the performance and latency depend on the interface specs, or on the CPU power only ?

Could you give me some advice on what to buy ? I read here a lot about the 828mkII, but it's really expensive here in France...