Just completed my first speaker modification, a full recap of my RTA-12B's. I decided to go with ERSE Pulse X metallized polypropylene caps after reading some favorable reviews on them, and I didn't have an unlimited budget. Total cost was just over $100 with shipping, only took me one night of installing them because I was so excited to get them in. So far, I've only got about 15 hours of power ran through them so I know I have more burn time to go but I can already tell a clarity difference and a stronger, tighter low end sound. I hope it continues to get better, which I'm sure it will.
I've been debating doing other mods, I've read many people dampening the inside of the cabinets, and using dynamat on the driver baskets. I've also heard that getting rid of the fuse will also help with extra clarity in the tweeters. We'll see what happens down the line but for now, I'm very pleased with the sound of these newly capped 12B's! Here's a few pictures of them. Hopefully that link works, if not I guess just copy paste it. Thanks!