Id suggest dropping the chunk on streetdeck now before you get too comfortable putting up with the free front ends. If you start with it right from teh get-go, youll never have to deal with convincing yourself to buy it later, and with mappoint included on the dvd, you wouldnt need to purchase streets and trips. Other than that, looks like the specs are pretty decent. Definitely upgrade that system memory like you plan. Good choice on the Holux, its what i have in my 04 WRX and works beautifully mounted under the clock pod, on top of the air vent with some velcro tabs. I even get a decent solid lock from several satellites from inside my garage with the door closed.
GOOD LUCK with your build, and please post some pics of the car and system!