The "over 500 Sun boxes" was not meant to imply one midrange. Each, loosely termed, application may have anywhere from 1 to 25 Sun boxes. Each Sun box cluster (even if only 1 box) is considered a midrange system.

The 1400 NT boxes are again either stand-alone or clustered to support applications. None of which are considered midrange. The USPS email system runs on NT boxes. (Special application prints out the email, puts a stamp on it and delivers in to your desktop ;-j )

If I were to call IBM for a midrange, I'd expect an iSeries (a.k.a. AS400).