I might be biased since I am selling AT's, but here's my response.
First, good luck finding those Audix's used. New they are pretty expensive (I think Full Compass had them for sale for around $400/each or so.. but check to make sure!). I know Sirchek has had "Sell me your audixs"in his sig for quite a while.
I think the Audix's are stealthable, totally. I've seen Ed's up close, and to me, they looked about the size of a really fat cigarette. A few people have added pics of a Kangol hat modified to run them ho's in DIN somewhere- that was pretty cool! Maybe Ed will chime in with his opinions, but I know John Kelly really digs his Audix's... other Audix mics I've used in multitracking situations have sounded really good too.
About the AT853Rx's, many people say they are great mics for the $. I liked them a lot... just wanted to downsize all my stuff for stealthing. They are versatile too. Depending on the model of Audix (and how old they are) they don't have switchable caps.