My advice, for what it's worth, is simple and predictable: Buy the 325s used, open them up and make the following low-cost mods:
1. Vent the driver backs (pop four holes into the felt behind the driver back, using a ballpoint pen to make the hole and the end of a mini plug to ream that hole). This will increase the airflow dramatically and you'll never find yourself complaining that these cans are too bright.
2. Get some gummy damping material, like Blutack or Dynamat and put a hunk of it on the magnet backplate. This will open things open dramatically.
3. Get rid of the plastic ring, down by the grill, as well a the plastic button that's stuck smack dab in the middle of your rear screen. These pieces of plastic add resonance of the worst kind. Getting rid of them will tame unnecessarily high-mid spikes, the kind that annoy the dickens out of you when you crank up the volume.
4. If you feel adventurous, take a steak knife, slip it under the driver cloth and rip it out (along with the spaghetti remnants). These are Grados. They don't need filters or anything else between you and the driver.
There are other upgrades you can make - from recabling to woodifying the front plastic chamber - but these mods are practically free and easy. In less than 20 minutes, you'll end up with the most amazing 325 you've ever heard - unamped. If you still feel like wood is in your future, there are a variety of after-market shells you can get as slip-ons. The RS2 is a bargain, compared to the $700 RS1 but at $500, it's significantly more expensive than a brand-new 325, which is significantly more expensive than a used one.
One thing: If you have a choice between the SR325i and the SR325is, get the "is." It has twice the cabling (eight-conductor cabling with a four-braid in pairs). More copper means more conductivity. I love silver but double copper is worth a lot more than the best silver. You'll end up with a thicker cable, and you may not notice much at the top end, but your bass will be significantly better. It'll have a thump to it that comes from the lowered impedance.