A 100 objects is a lot. Whatever machine you'll buy, the loading most likely will not speed up at all. Unless you're going to use a solid state hard drive, but that would be kind of throwing away money.

aRtBee has some good advice and I like to add something to it. with such a scene I can image your preview being slow, there's a lot to handle by your graphics card. Go into render settings and select the preview tab. There's a feature called Texture Display and bring the number there down to 256 or even 128 if needed. Also make sure Enable Harware Shading is off. That should speed up your display a bit. You can also go into your graphics cards settings program/drivers (not sure what that is for Nvidia, only have ATI) and set the 3D settings to speed instead of quality. Standard it's set most likely to balanced or so, but go for speed in this case. You can set it back later when done. That helped me a lot to get rid of the slowness is some scenes.

Then there's the i5...... it isn't the best rendering cpu there is. If your motherboard can handle a better then go for it I would say and adding more memory is never a bad idea. But you have to ask yourself this question first..... is this a one time project or will it happen much more often? If it is something you'll do occasionally then don't bother doing all kinds of upgrades. If you are struggling with your system more often then consider saving up for something new or better.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk