Recently, I splurged and spent $1000 in math textbooks in preparation for the Mathematics GRE subject test. So far, in terms of calculus books, I have purchased Spivak, Stewart, and Baby Rudin.
Is this sufficient preparation for the Math GRE or do I need to get my hands on Apostol?
FYI: I am extremely familiar with the univariate calculus and real analysis material. Multivariate, not so much.
Stewart's Calculus will prepare you for the calculus questions in the GRE, while Rudin's Principles of Mathematical Analysis will prepare you for the introductory real analysis questions in it.