So, this isn't the most straight-forward way to get the prices, but if you're like me and have to wait to buy a shiny new reader (sadly, for who knows how long...), or are okay waiting a couple of weeks, then I figured I would share. Also, I think it might be US specific, but I could be wrong - as a disclaimer I've never actually bought from them.
(And if it's common knowledge, oops. I tried.

)
Okay, so if you join
Sony Rewards, you can then subsequently also join the Wheel Watchers Club. Every weekday you enter the answer to the bonus round on that day's Wheel of Fortune and you earn 10 points, as well as being eligible every time for a random trip giveaway, as a bonus. After you've answered I think 10 of them, you get to the Free Spin level and now get 10% off everything in the catalog if you shop through Rewards. If you answer another few (I think it was 15 total? I just hit it the other day but it could have been 20.), then you move onto Jackpot status and everything is now 15% off.
Going through the catalog, this now makes the 300 go from 19,999 to 16,999 points and the 600 from 29,999 to 25,499 points. Points are valued at $0.01 and it says that you can purchase what point you may be lacking for that price as well.
So you get them for $170 and $255. Actually, you'll end up with 150 points or so just to make it to that level, so there's an extra $1.50 off too.
Don't watch Wheel of Fortune? Me either. Thankfully there are
blogs that post all the answers, everyday.
So, it's a little more complicated than a coupon, but the 15% discount is on everything, should you also be in the market for a laptop or something. Not bad for taking two seconds of time for a couple of weeks, in my opinion.