Expandable, 4 ins, HQ Interface?

[ZenLizard]

Modular, 4 ins, HQ Interface — That's what I'm looking for, with 2 or more outs. I'd like to have 4 inputs right now and add an additional 4 later on. Is there a brand and model anyone knows of that fits that bill? It must be iPad/Auria compliant, of course. It would be nice if the iPad could be charged during use but that's not a deal breaker. It could also be 6 ins I suppose, or 2, as long as they can chain to each other for simultaneous use.

Thank you to anyone who may provide an answer.