So I'm pretty new to this as well, and I've been trying to learn what's out there as well. Old hats, feel absolutely free to correct me if I'm wrong. My observations thus far. The three basic things that people seem to go after quickly is the sprocket change, a new spark plugh and a better air filter, typically K&N. I've found mixed reports on the plug/filter thing, some people have ran into trouble.
Ace seems to be the undisputed man as far as tuning goes for RE, but most of his stuff goes over my head, tech wise, and I haven't found prices on any of it to even know if it's practical for my budget. I'm digging through his Ygroup now, trying to learn more. seems to be a goldmine all the same.
If you are able to trade in later this year, you can get the new Cafe Racer model which....
You'd have to sell your bike and buy an Iron Barrel model as a basis, and then....
I know this is a relatively inexpensive bike, which is one of the draws for me. But it's not so cheap that I can afford to just dump it and start over.
If money isn't an issue, check out the v-twin conversions. One is called the musket, at
www.musketvtwin.com/ the next is the Carberry at
http://www.carberryenfield.com.au/ and the third I've found is the Norcroft at
www.norcroft.co.uk/. US/AUS/UK respectively. The musket isn't available yet, and the carberry requires a deposit that is higher than the new bike costs off the show room floor.