Can anyone tell me what makes this different than the standard mazda3?

 

The sp23 was a special edition model for '05. That said most of the "special" features were either available with other packages, or became standard on the following '06 model GT trim.

The main things:
-carbon gray mica paint (only time it was offered in the US)
-LED tail lights (hatchback only)
-high gloss wheels
-option of saddle brown leather
-piano black interior trim (I think this was also on the '05 i model as well)
-Bose stereo
-cabin air filter

Most of them also had the HID/TPMS package, and I think came with the SAB/SAC/ABS package.

 

Jayjugaus, where in the world are you? Different countries have different specs.