I've never upgraded the crossover components so somebody else will have to comment on that mod.

The one thing that really did improve the 2 Pi Towers (to my ear) was adding duct seal and felt to the driver baskets. Played with this a bit and the best improvement came from putting lots of duct seal on the front and back of the woofer baskets. Then the front of the basket (facing the woofer cone) got covered in felt. Don't leave off the felt as it REALLY makes a positive change (without the felt the speakers sounded a bit lifeless).

The tweeters also got a gob of duct seal on the back plate. That seems to help, too.

Felt and duct seal costs about $6 to $8. It made a truly positive improvement (in my opinion) and can be removed if you don't like the results.

I believe the sound is far more refined with the mod. It took away a bit of midrange to upper midrange hash/glare that wasn't realistic. The 2 Pi's sound damn fine now.

One warning, the edges of the woofer basket are fairly sharp. Don't cut yourself on them like I did.