You may want to use a virtual machine of Snow Leopard Server, so you can do everything on the new one you do on your existing 17 MBP and run CS4 on a 2015/2017 MBP with Sierra and High Sierra. With VMWare Fusion, it will be easy to run Snow Leopard on a brand new machine, and with a 15-inch you will have enough power to run more intensive Apps.
If that is something you wish to do, a dGPU 15-inch is arguably ideal. If you go 2015, I recommend a dGPU model over an integrated-only model. From most reports I have read, the R9 M370X dGPU in the 2015 seems to be about the same as the base Radeon 450 GPU on the 2016 MBP15. The new 2015 models available directly from Apple are iGPU-only, but Apple had both the high-tier and BTO 2015 MBP15s with the dGPU available refurbished for a very reasonable price. It is a great buy for a great system.
2015 15-inch MBPr with dGPU + 2.5 GHz i7
2015 15-inch MBPr with dGPU + 2.8 GHz i7
You can't go wrong with the current model either. If you do go for the current model, upgrading to the Radeon 560 is a good investment IMO.
From a transfer perspective, you can do a direct transfer via Thunderbolt or FireWire, a backup to an external hard drive followed by an import of the data on the new machine with Migration Assistant, physically removing the hard drive from your current system and putting it in an enclosure and plugging it into your new machine and manually importing data, or transfer files via WiFi. (If you buy a new MBP after High Sierra releases in the fall, the best practices in terms of restoring data may change because Apple will have changed over to a new filesystem, and this new filesystem could be the one used by default on all new Macs.)