More RAM is certainly a good idea - 4Gb isn't enough. However! A poster above said he'd reserved 25Gb for a RAM disk, which only leaves 7Gb for the OS and other applications. Lightroom uses a ton of RAM, and if it runs out it'll start using the pagefile, which means hitting the hard drive, which gives a big slowdown. With 32Gb of RAM there's no reason not
to use a RAM disk, but personally I'd leave a little more available for applications to use and have a smaller RAM disk. However, this is one of those things where experimentation will find the best sweet spot.
1.7GHz Core i5-2557M processor
This is going to be your second bottleneck after RAM. Lightroom is very CPU heavy (more so than Apple's Aperture, which offloads a lot more work to the graphics card than Lightroom) and I'm noticing my computer (which has a 3.2GHz i5 CPU) bogging down sometimes with 18MP pictures from my 60D when I'm doing batch edits and such.
Also, I looked up the spec sheet of that CPU (here
) and it says the CPU only supports up to 8Gb of RAM. I'm not sure if that's true, but you may wish to double-check before throwing RAM at it.