Hey man,
I think I can help you. I recently upgraded my mics and pre from AT822 > AD-20 to SP-C4 > UA-5. The AT822 is a great starter mic, and the AD-20 was a relatively cheap pre/AD Converter that worked fine for the AT822. That would probably cost $300-$400 total, depending on cables and other stuff you'll need, too. I did a lot of great shows with the AT822. It was extremely easy to use, and the battery lasted forever. The mic is noisy and a little tinny, but not bad in loud bars where it is noisy anyway.
If you can budget closer to $1000, the C4 and UA-5 are both light years ahead in terms of sound quality. There are a couple things you need to know. Make sure you get a digimod UA-5, and make sure that the mod was done by the Oade Brothers. The Oades also offer other mods (i.e. upgrades) to the UA-5, but the will only upgrade it if it was a unit originally sold by them. You need to have the digimod in order to be able to use the unit's Coaxial or Optical out without using the USB out. That means, unless you are recording with a laptop, the factory version of the UA-5 is useless. The digimod rewires the circuits so that the Coaxial and Optical connections are active without the USB being active. Other people have modded these units themselves, and there are actually instructions here to do it yourself, but the huge advantage of the Oade modded UA-5 is that you can send it to them for the upgrades in the future (at a cost, of course, but well worth the investment, IMHO), and these are mods that you cannot just find instructions and do yourself, so if you don't have an Oade model, you can never get the upgrades.
The C4's are wonderful mics. There is a huge sound upgrade from the AT822 to the SP-C4s. The difference between Cardiod and Omni mics is that Cardiods are directional and Omnis are not. In other words, the Omni will record everything in a 365 degree circle around the mic. The Cardiods will record what in front and to the sides, but not in back. It's nice to have both caps in one set with the C4s. The AT822 is cardiod only. The C4s come with a t-bar and shock mounts, but not a stand or cables.
Anyway, good luck. I highly recommend the SP-C4, UA-5, and JB3. That is a great starter setup, if you can make the investment.