Am willing to spend some serious $$$ on the right tools that the PC repair pros use as I am planning to start a repair service. Links, opinions or recommendations wanted, please. Already A+ certified with 20 years in field. Thanks.
Personally I'm not a fan of commercial Software for computer diagnostics. I'm not saying they are bad or so I just haven't found any that I couldn't replace with a free alternative.
For example you can grab the IntelBurn Test (and a few other burn-in tools at the following link:
Alternatives for AIDA64 could be (depending on the features your looking for):
http://www.gtopala.com/siw-download.html (the older SIW 2010 is freeware now)
I admit Smithmicro CheckIt offers a lot of functionality within one tool but again, there are alternatives which can do the same. You could grab Ulimate Boot CD (UBCD) which offers pretty much everything you need.
You can get a decent monitor (TFT) test directly from EIZO
But again, it's up to you which one you prefer to use.
Sandra 2011 is a good one. I've used previous version in the past for burn-in testing, analysis, and general diagnostics with excellent results. They have an Engineer version for commercial use in repair shops that is licensed per technician, not computer.