Yes, you will be amazed how fast it will be with an SSD! I think, for everyday use, switching to an SSD from HDD is the biggest speed jump... - at least what you can feel and not only the benchmarks... - I would recommend a 128GB Samsung 830 or 840, now they're pretty cheap/less expensive and they're very good...
Now, I could not find your PSU... it really does matter which exact model do you have... your graphics card may need more power than the PSU can supply on the rail... and I'm thinking here about the amperage... - so, if you can not find the exact model on it, try to search the internet... a link with the product page from where you got it would help... (also, would be nice for the graphics card too)