Sorry to drudge up an old thread, but just FYI the TS-9 and TS-808 are nearly identical circuits. The only differences are the Opamp IC thats used (about $0.50) and two resistors (about $0.25) in the output buffer section.
The TS-808 uses a new production JRC4558D opamp. The TS-9 uses a few different chips (TA75558P is common). By modern audio standards, the JRC4558 is actually a pretty noisy and crappy part. It was chosen most likely because it was super cheap and in plentiful supply. As the years went by, the JRC4558 chip was eventually discontinued and a newer, higher spec'd replacement was used in the TS-9 reissue pedals. Even though the replacement chips were cleaner and better by audio standards, people prefered the sound of the old JRC4558 chips, and so the "vintage" tubescreamer lust began. When Ibanez got arround to re-issuing the TS-808, they went back to the JRC4558D chips, as they were once again being produced. By the way, the Opamp has a fairly small impact on the distortion of the tubescreamer. Silicon diodes are used to generate most of the clipping. Swapping for some different ones can give you some different shades of grit and grind.
As for the two resistors in the output buffer section, basically all they do is allow the TS-808 to drive your amps input a little bit harder. Both of these changes are fairly subtle. In a blind listening test, you'd have a tough time picking out which was the TS-9 and which was the TS-808. Basically all this means is, Ibanez is making a killing on their TS-808 reissue by taking a TS-9, changing only a couple of super cheap components, slapping it in the vintage style case and adding an extra $80 to the price. By the way, the TS7 is also nearly exactly the same as well. You can pickup a TS7 for about $35 and change a couple of components and have a TS-808 for WAY less. The Boss SD-1 (about $40 new) is very very similar as well, and can also be moded to TS-808 specs with just a few component swaps. There's tons of info online about building and modding pedals. Read up and have fun with it. The TS-808 clone on my board cost me about $40 in parts.