There are definitely upgade kits to put extra halo rings on the non-angel eye lights (from 2000 MY and before), however it is messy and one can definitely tell there are not the OEM Hellas but rather DIY. Also, I know people who have began getting water and condensation issues, since one needs to open up the lenses and related parts and even if you put it back together again in the same order, there is a risk of water leaking through.
I just upgraded mine to the European Clear Corner OEM Hella AEs and the look is really awesome (especially on dark cars such as the Carbon Black). I got mone from Bekkers for under a grand in only 2 days - excellent service, packaging, the whole deal. You can get the US DOT approved (with Amber side reflectors) for a $100 less, but the look is not as clean in my opinion. These came with all the necessary harnesses which alows for a very easy and quick instal (no splicing or mods necessary). Also, be aware when you are buying from some other places, because sometimes Xenon bulbs may not be included (even though you can use your existing ones, I found the newer ones to be clearer/stronger [perhaps the new scratch free lenses had something to do with that as well]).
Lastly, there are some sites selling the Demon Eyes setup - same as Angel Eyes, except much much brighter halos (they are almost a headlight in itself, perhaps using xenon-type bulbs!). Two major drawbacks: they are not OEM (not Hella but rather made in China/Korea/Taiwan), and you will loose the auto-leveling feature. There are a few Beast owners on the Board that have posted pics, look really good, but for me the 2 negative factors I mentioned outwieghted the one benefit.
Good Luck! You will be happy either way you go.