Yes, I currently use my ipad for reading books borrowed from my library, using overdrive. I'd prefer to read it on my kindle, tho, generally. It's not the end of the world, just a preference.
The smallest mbp has a lower res display than the mba, if that matters to you. It also doesn't have the better graphics chip. But it does have thunderbolt. Thing's a giant behemoth tho, compared to the air.
You have a working amp. You're asking for help diagnosing a problem that doesn't exist on a forum where the members are openly hostile. What is the problem you're trying to solve, and do you think you're really the person to solve it?