Should I buy "Aristotle SC" or should I stay with Manhattan SC?
-- Manhattan SC is one of the bests book out there for SC. Its certainly a good reference.
Should I incorporate Manhattan Advanced quants? ( I am not done with all the Manhattan quants books yet)?
-- It depends upon what is your target score in Quant. Once you finish your
MGMAT quant books, Give a GMATprep or
MGMAT test first and find out where do you stand in Quant.
If you want to score 50-51 and are consistently scoring above 47-48, then
MGMAT advanced quant is for you.
If you are scoring in lower 40s then you would need to work more on the basics through
MGMAT strategy guides.