2007 honda element sc system

Just made the initial purchase today for the 2007 Honda Element SC.

2-15" Rockford Fosgate T1 subs, Rockford Fosgate T10001BD. Still haven't decided on enclosure yet. Looking at slotted but not sure with space constraints. Will be upgrading the big three, optima battery, and a band-aid(5farad cap). I'm keeping the factory head deck for the xm radio and the ipod hookups. So I will be adding either a JL Audio Clean Sweep or Rockford Fosgate 3Sixty.1. I think I got a pretty good deal, the subs for $500 pair and the amp for $475. Oh the 5 farad stinger for $125.

Just had a few questions for you.

First, from my readings on here I can upgrade my factory alternator without effecting my electrical system? The BD10001 has a 150amp rating and I will be adding another amp for mids and highs shortly after. So, I'm figuring at least 150amps for the system due the fact that I'm pretty sure the 150 rating on the amp is at peak. So its not gonna peak at all times. So I was thinking of upgrading to about a 200amp alternator. Sufficient enough to handle the load?

Second, after upgrading the alternator, would you recommend upgrading the battery or would the factory battery be sufficient?

And last, anything else I should be looking at when going for SPL?