You look like you have your goals set. Instead of putting money in D series, I would go B series as well. ( or even K series if you can find a good deal on a type-s swap)

There are people with low 12 second all motor d series, but they have nitrous and the car is pretty gutted.

Try to set a HP goal and make up a list of expenses and add everyhting up. You will suprised sometimes...

For example, when I started working on my gsr block, I wanted to do it the right way.. So the block got hot tanked, the rotating assembly got balanced, I got APR bearings, OEM pistons, rods, etc... Once I got everything, I was way off what I thought it would cost me... So I sold everything and moved on to a more cost effective project... :P