You will see a big difference. I did the same thing, upgrading from a DD50 to a Fatty Ultra 70. I did this on my own, no trade in and paid $250 used (barely). Comparing the $369 to upgrading to a new 80mm fork other than a headshok would include $80-100 for a reducer headset, leaving you with $270 or so to put toward a fork. The headshok you would be getting would be a better product that a fork in this range unless you find an awesome deal on a 05 closeout. Headshoks normally retail for over $500 last time I checked.