Ok, thanks Fegari - that should make PS run pretty well and should take care of rendering previews in LR in library mode. The remaining constraint I guess you will have is rendering LR previews in Develop mode which will still be constrained by read speed off your files disk which is presumably a mechanical drive.
With your configuration, do you find there is benefit to adding more memory or have you lessened the requirement for high memory with your SSD's. Thanks and Regards.
I have LR, Photoshop and the OS on my primary SSD (128GB). The lightroom catalog files, ACR cache, and the photoshop scratch disk go on a second SSD (also 128GB). Image files are located on a fast 2TB hard drive.
I don't find that LR needs much RAM at all. My old system only had 8 GB and LR never would use it all. My current machine now has 16GB and that's more than enough. The only caveat is that when you use LR and Photoshop together, Photoshop can use up all the RAM and leave none available. This will adversely affect LR's speed if the RAM usage hits 100%, even if you have a fast scratch disk. So my recommendation would be to get enough RAM to cover your Photoshop usage so that Photoshop doesn't step on LR's toes, so to speak.
I don't think that your comment about the Develop module being constrained by a traditional hard drive is necessarily correct. While I'm sure it has some impact, the main thing that is happening in the Develop module that the CPU is rendering the image data from the RAW file. The time it takes for the CPU to render the data is significantly longer than the time to pull the data off the hard drive. The CPU rendering time might be between 2-3 seconds for a 20+ megapixel file, where the time for the data to be pulled off of even a slow hard drive is under half a second. The real bottleneck for rendering previews/importing/exporting/develop module is going to be the CPU speed.
That said, I do try to optimize my system so that disk speed is not an issue. On my 2TB storage drive, I partitioned off the first 100GB where the drive speed and transfer rates are the fastest (due to the rotational platter/fixed disk head design of a traditional hard drive). I use that partition for importing and working on my current photo projects. Once those are done/keyworded/exported, I'll move the files off to the remaining portion of the drive for longer term storage where speed isn't as important.