IME P95 and OCCT in there various configurations provides the best stress testing of both the CPU and RAM. ITB and Linpack are mostly a CPU stress test. The "blend" in P95 and "large data set' in OCCT are the best overall test. The "small data set" options stress mostly the CPU - similar to IBT/Linpack. OCCT also offers a GPU and PSU stress test. Any reliable PC will pass all of these stress tests though ITB and Linpack are some what redundant if you use either P95 or OCCT.

If you get errors in any of the above tests and you have not already recently run Memtest86+ for 6+ hours without errors, you should do so as I am seeing a number of brand name RAM kits failing in as little as 2 weeks to a few months when run at their rated frequency and voltage.