Quite simply the only difference between the Rad9500 and the Rad9500PRO is the nonPRO has 4 pipes while the Rad9500PRO has all 8 pipes just like the Rad9700 series, this effectively boosts you from Rad8500 perf to GF4TI4600 perf as a rough guide. Clocks are identical for Rad9500, Rad9500PRO and Rad9700, here's a summary...
Rad9500 -> 275/270 w/ 4 pipes & 128bit DDR.
Rad9500PRO -> 275/270 w/ 8 pipes & 128bit DDR.
Rad9700 -> 275/270 w/ 8 pipes & 256bit DDR.
Rad9700PRO -> 325/310 w/ 8 pipes & 256bit DDR.
All 3 of the cards clocked at 275/270 should hit between 325/290 and 360/350 but the 4 pipes on the Rad9500 will REALLY hold you back. One site even managed to get a Rad9500nonPRO based on the 9700PCB with 128MB so using the full 9700 style 256bit DDR BUT with only 4 pipes, this meant that even with an o/c from 275/270 to 400/310 it still struggled against a stock Rad9700nonPRO, and all Rad9500PRO with 8 pipes tend to hit Rad9700 perf even with 128bit DDR.
Of course you MAY find that Rad9500nonPRO will use the worse RAM and/or cores, they are targetted at the OEM market because they don't offer perf any where near the higher Rads inc 9500PRO. The 9700PRO should o/c even better because it should use slightly more capable RAM but with a simple BIOS flash the Rad9700 makes much more sense.