2-4 cu ft isn't giant in my book. Things like Klipsch Cornwalls are the starting of giant. Then again I have a 4.5 cu ft and a 12 cu ft sub enclosure in my room.... But the DSP is more for crossing low where a passive XO would need massive inductors... And boost eats headroom. Use a decent wideband/fullrange mid and cross the woofers low and the tweeters high.
I still think a folded TL with dsp to fix the ripple would be awesome though.