The first thing you should do before going down the upgrade path.. not to be rude or anything, is to get the engine fully checked out, compression tested, leak down tested, turbos checked, etc. Timing belt replaced, oil flushed, etc. That may set you back $1k, but it will be piece of mind.
But before spending all the money you have on mods, just make sure the basic mechanicals are not likely to go, or no signs they are developing signs of weakness. No point going for massive power when cylinder x or something is already way down, as its just going to blow the engine that much more quicker. Once the mods go on, and maybe something big goes.. that $6k might be needed.
That's what I'd be doing. Once you've done that and sure you have a good base to work with -- go sick!