Well, the low end SSD's aren't as fast as you probably think they are. Although the latency is significantly lower than platter hard drives. I don't think you would really see any difference in your case. You could get 2 hard drives in raid and have good performance. But I am currently happy with my single hard drive and have no issues with speed.
Its really up to you I guess.
I would probably switch the PSU for something from a more reliable company, maybe OCZ or some sort if you are looking for a cheap PSU.
Something like OCZ