I did a few quantitative tests from 800score.com and those were definitely harder than the stuff you'll be seeing on the actual GRE. But you should still get them as they'll make for good practice (also the actual GRE will seem easier after doing these tests). Don't worry about the scores they give you - you'll get at least 100 more on the GRE.
I can't say anything about CatPrep.
hope this helped.