Welcome to the GMAT Club
Well Yes Manhattan Gmat
tests are good no doubt.the quant part of MGMAT tests is bit harder rest its the next best tests available for GMAT preparation.i will advice to not just simply buy MGMAT tests.Buy Any one MGMAT book
of ur likes its 26$ and u may get some discount on it ..MGMAT tests are free with purchase of any MGMAT book
..while the test seperately are available for 39$
Good part is explaination of tests with answer is gr8!!MGMAT SC
is Gr8 If u dont have it rest u can see for number properties or any other.
Apart for MGMAT the other tests if u wanaa try is 800 score tests they are also good.
If u specially wanna focus on ur quant section for good 700+ level questions u can try GMAT CLUB tests
Also apart from all this u can take one diagnostic test free of knewton,veritas
...although these dont offer their full practice tests seperately...
I hope it helps u!!