The big difference in the 661 and the other two decks is that it provides phantom power (48V power to the mics) while the other two do not; it is also much bigger. For small mics like the CA-14 than run off of a 9v power supply, phantom power is unnecessary. For most larger and high-quality mics, phantom is necessary (there are devices like the tinybox that do not provide a full 48V but can power the detached capsules of some mic systems, but let's just keep this simple right now).
it sounds like what you want are small mics. If you're stealth taping your main options are the Church Audio line and related competitors like the AT853, the Countryman omni mics, the Nevaton omni mics (which require 48V phantom), the Audix mics with Church cables (all of the foregoing at or just under $500) the DPA 406x series omnis ($1000 new or ~$650 used), or various types of mics that require 48V phantom and cost over $3500 new/$2400 used (DPA, Schoeps, Neumann). You'll note that of these options, a lot of the small stealthy mics listed are omnis, which are somewhat less flexible in terms of where they can achieve optimum performance.
*if you like the sound of them* I'd at least consider the Audix. They're tiny when run with a Church cable (same size as the CA-11) and can be run with a little battery box; if you buy the bodies, you can use those for open taping using 48v phantom. A new set of Audix with the bodies is under $1000 and the Church cables are $65, plus another $40-60 for a 9v battery box.
There are forthcoming options like the tinybox with various capsules such as the beyerdynamic ck930. That may also be a good fit but people have not seemed to have tons of succcess sourcing the caps alone. There is also a much frothed about AKG option with the tinybox which would allow you to run AKG ck6x caps directly into the tinybox, I believe. That would probably be where I'd go in your price range, if and when the product actually comes out.