so if ever I get through with it, what interface and DAW should I use?
Macs usually have garageband if you get the complete iLife option I think, but Logic is a far better DAW for Macs, IMO. It IS expensive to get the full Logic install, you might want to try Logic express but at 10k or something, I would rather save up for the full Logic.
An alternative is to get Pro Tools. The newest version is native, which means you can use any hardware with PT. For audio, PT is a battle-tested solution. For composing, Logic is the better choice on the mac platform.
You still won't go wrong with Windows based laptops. Also it's more affordable.
Agreed. But the better way to approach this is to "let the software decide what platform you will use".
Obviously, if your main DAW of choice is Logic, then you have no choice but to go mac. But if you use Cubase/Nuendo, Sonar, Live, etc., going windows is just as good, and you may even get a machine that is faster. For me, mac pricing can be ridiculous at times, but what you really pay for is platform stability... it just works. Personally, I prefer the tweakability of the windows platform.