If you are using a HDTV DirecTV receiver that also handles OTA HD signals, then the built-in tuner in the XWX series does not do you much good. If your cable company is using unscrambled QAM for its HD channels you should be able to use the builtin tuner for that. THE XWX does include two...
The XWX uses the same same CRTs as the SWX. The XWX has a built-in ATSC tuner and a better anti-reflective screen. Given the same source material and a controlled light envioronment, the picture quality should in theory be identical.
The TWX series has a better anti-reflective screen than the SWX. Other than that, and the faux marble cosmetics you mentioned the TWX and SWX are identical. The UWX uses different CRTs than the SWX and is considered a lower end model than the SWX/TWX.
In the fall, when the new TV model year begins there will probably be more, but for now RCA and the Hitachi XWX series are it, and if I'm not mistaken the RCA IEEE connection is only one-way. But for now, I think the Hitachi 57XWX20B might be what you seek. Its a bit more than 3000 though.