> 9800GTX+ (for some reason the drivers identify it as a 250GTS)

It's because it's the exact same card. On most rebrands, at least they bother to change the relevant identifiers, but 9800GTX+ differs from a GTS250 only by the number on the box. As such, the drivers have no way of knowing which of them you have -- they cannot even make a solid guess from batch numbers because unsold 9800GTX+ were repackaged as GTS250's. Faced with this, the driver programmers decided that less people would probably complain if they just called all the cards by the latter name.

Fun fact -- differently harvested versions of the G92 chip have been sold as:

     - GeForce 8800 GT   $2
     - GeForce 8800 GS   $1
     - GeForce 8800 GTS
     - GeForce 9600 GSO  $1
     - GeForce 9600 GSO ASUS 512 $$
     - GeForce 9800 GT   $2
     - GeForce 9800 GTX
     - GeForce 9800 GTX+ $3
     - GeForce 9800 GX2
     - GeForce GTS 150
     - GeForce GTS 240
     - GeForce GTS 250   $3
     - GeForce GT 330

Groups marked with $n are all exactly the same card, with no differences whatsoever. Many other sets have only very minor differences. $$ denotes the biggest ripoff award -- halved memory bus width and cheap memory make this card only half the speed of the normal 9600 GSO.

So, if you wonder why NVidia is swimming in cash, it's because G80, and it's slightly modified shrink G92, are insanely good designs. G80 debuted in late 2006 and G92 in late 2007, and it's still selling.