Since the Heresy IV isn't out yet and there are no specs on the Klipsch site yet (that I could find), it's a bit of conjecture. I think I read in one of the threads about the Heresy IV that it will be a ported model, so I think you would have to do more work than it's worth to take a II to a IV.
The II is well regarded, and many seem to like them better than the III. You can buy aftermarket crossovers (or kits), and can replace most of the drivers. Bob Crites offers great parts at reasonable prices. There are some other options for aftermarket crossovers for Klipsch speakers designed to "improve" the sound (not sure about the Heresy II). I have stuck with Crites parts. I have upgraded my Heresy I by replacing the woofer, tweeters, and crossover, and putting Dynamat on the outside of the horns.
As someone else said, give them a try stock, mine were very nice when I bought them, and they were about 40 years old when I got them.
Klipsch has forums with a ton of information about upgrades and mods.
The II is well regarded, and many seem to like them better than the III. You can buy aftermarket crossovers (or kits), and can replace most of the drivers. Bob Crites offers great parts at reasonable prices. There are some other options for aftermarket crossovers for Klipsch speakers designed to "improve" the sound (not sure about the Heresy II). I have stuck with Crites parts. I have upgraded my Heresy I by replacing the woofer, tweeters, and crossover, and putting Dynamat on the outside of the horns.
As someone else said, give them a try stock, mine were very nice when I bought them, and they were about 40 years old when I got them.
Klipsch has forums with a ton of information about upgrades and mods.