konichiwa I'll give it a shot, but I stopped reading that thread after about post 60. I'd seen all I needed to see to figure out what was going on and concluded ATi was too lazy to differentiate their parts and regulate what their OEMs were doing
OK, now that I got my little jab at ATi in there,

I'll try to explain it the way I see it:
1) The core itself on the 9500/pro and 9700/pro are identical (all full-blown R300 by design); there may be SOME binning going on at ATi, given some of the mod failure rates and inability to achieve stock 9700pro speeds. More on this later.
2) The ONLY physical difference between a 9700 vs a 9700pro SHOULD be the memory speed. The PCB, memory interface, pipelines, core, basically all the guts are the same. Through the use of preset BIOS default core clocks (locking them at what you could call an underclock) and
different rated RAM, ATi differentiates between the Pro, non-Pro, and "Gold". This is not uncommon, as nVidia has been differentiating their product line for some time using this strategy (we see it to some degree with CPUs as well, with various steppings producing similar speeds as higher rated chips).
This is where the 9700 and ATi's poor quality control benefits
YOU 
We all know that Sapphire is ATi's major production partner. Well it seems their friends over in Taiwan have trouble keeping track of which card is supposed to go in which box, so they just slap the appropriate BIOS lock on their 9700's and ship em out the door to you!!

So what you end up seeing is a BIOS locked card, with both underclocked RAM and Core, selling for $100 less than its identical siblings. Get yourself a hacked BIOS from Rage3d.com, flash your card, and you've got a full-blown 9700pro. Of course this will ONLY work if your 9700/Gold do indeed have the 2.8ns, most other OEMs do use cheaper RAM. Otherwise you'll still end up with an unlocked card that will be able to unleash the full speed of the core; the RAM will still be limited and may not approach stock Pro speeds.
3) The 128MB 9500 non-pro is very similar to the 9700's, except it does have physical alterations/differences. First of all, it will have slower RAM, probalby 3.X Hynix vs. the 9700 pro's 2.8ns Samsung. If we remember the "differences" between a 9500/pro and the 9700s, the 9500 has 1/2 the rendering pipelines AND 1/2 the 64-bit memory controllers of a 9700. Since we KNOW the cores are R300, its not a core difference, its something external. Well, guess what? The 128MB 9500 happens to have the same PCB as the 9700's, with its 4 memory controllers intact (64-bit x 4). All you need to do is enable the disabled 4 rendering pipes, and you've got yourself an un-neutered R300 core. This is done by either physical moving a resistor, or hardmod (similar to unlocking an Athlon), or doing one of the softmods (I haven't looked into the specifics of how these work, but there are a few ways). Again, your results will vary depending on the PCB-type you get, and you probably won't reach the OCing limits of the Pro's b/c of the memory (and possibly core binning). Guess who makes the one you want? You guessed it, Sapphire

. Again, I mention possible binning, because there is a fail rate on both the softmod and hardmod when all 8 rendering pipes are enabled. Results are artifacting and errors, indicating the core is imperfect and the enabled pipes are defective. This is why I suggested going the 9700 route, you limit your risk.
4) The 9500pro is kinda the odd-man out here. Its got a full-blown R300 with all pipes intact running at full 9700 clock speeds and with fast RAM, but it doesn't have the PCB with 4 memory controllers (some might, I dunno, I stopped following up on it). IIRC the distinguishing features are whether or not all the RAM modules are on the front of the card.
Here's the 9700 you want for the BIOS mod - Note the user comments. This card has gone up $7 in the last few days, as I'm sure Newegg's usual forum lurkers have made note of the latest hot items and adjusted prices accordingly
Here's the 9500 128 MB version that could be softmodded - I'm no longer sure if this works, as there is a new "black" PCB version stocked. This may very well be the Grim Reaper from ATi in the form of a PCB revision. I would wait for some user feedback before going with the "black" version, but some retailers may still have the red PCBs that look IDENTICAL to the 9700 PCB.
Those of you that know more about the topic, feel free to correct me, as my post is laden with sarcasm and personal insight.

But I think you'll find most of it is right on other than specifics of which card is capable and which is not.
Chiz