It's the same format but using GTX and three digit. The first digit describes the generation (2xx, 4xx). Second and third digit can be described as the tier (such as your x900 and x800 description). So a GTX 4xx card is more recent than a GTX 2xx card. A GTX x80 or x85 can be considered best single-GPU. Then it trickles down to other tiers such as x75, x70, x65, x60, etc. The only new placement is that "x9x" is saved for dual-GPU cards, such as the GTX 295.