Sounds like you have some serious constraints in space, tow vehicle and willingness to register and insure a second vehicle.
What's wrong with the Boxster? Not fast enough? Sure you can hop it up for track duty without making it useless as a daily driver. If you don't want to take out weight, put in more power. You can do a lot for 10k.
I have seen some engine donations from the 996 that looked like a fun project and a potent car when finished.
Or sell the boxster for a newer boxster S.
George