CS3 is totally out of any upgrade loop now. You are free to buy Photoshop CS6 Perpetual License as a full version, $700 for the standard version or 1 cool $1,000 for the extended version of Photoshop or subscribe to any of the subscription plans for CC, CC2014 ($30 a month) or the Adobe Photography plan ($10 a month), but then you never get to own the software; the moment the monthly or yearly payments stop, your software ceases to work.
Just a clarification in general:
Remember, you are not addressing Adobe here in the user forums. You are requesting help from volunteers users just like you who give their time free of charge.
In other words, please don't kill the messenger.