There is a big gap between lvl 2 & 4, and to make that jump from 4 to 2 directly is not recommended unless you have a sound command in Kanji and intermediate grammar. If you go to university you can expect to achieve that level in 2 years of study.
Level 4 is pretty much a waste of money. The only thing that you could do with the level 4 certificate is that you can tell others who don't speak a word of Japanese besides "konnichiwa" or "ohayoo" that you know a couple more Japanese words than they do. On the other hand, the preparing for the level 3 should give you a thorough basic background on the different aspects of the language (although I cannot say you can survive in Japan with level 3 Japanese)
Use the kanzen masuta series for level 1,2,3. They can be ordered at amazon.jp
Also, for listening, you can try the nihongo journal. From what I know, they are starting to publish new editions again.