What is the best tuneup software for a iMAC?

Any software, no matter where it comes from, that purports to automatically "clean up" or "speed up" a Mac is a scam.

It's best to describe the functional problem, if you have one, in as much relevant detail as possible, rather than to say what you think is causing it or how you think it should be solved.

... Dose anyone have real experience with these packages that can tell me how I can speedup my Mac and get rid of unwanted cash and system files?

Yes. I have personally evaluated most popular examples of those products. They are scams.

Excerpted from Effective defenses against malware and other threats:

Never install any product that claims to "clean up", "speed up", "optimize", "boost" or "accelerate" your Mac; to "wash" it, "tune" it, or to make it "shiny". Those claims are absurd.

• Such products are very aggressively marketed. They are all scams.
• They generally operate on the flawed premise that a Mac accumulates "junk" that needs to be routinely "cleaned out" for optimum performance.
• Trial versions of those programs are successful because they provide the instant gratification of greater free disk space.
• That increased space is the result of irreversible destruction of files, programs, or operating system components normally protected from inadvertent alteration or deletion. The eventual result will be unreliable operation, poor performance and random crashes that may not become evident for months or even years after their use, when updates to programs or OS X are eventually released.
• Memory "cleaners" that circumvent OS X's memory management algorithms work by purging inactive memory contents to mass storage, which can only result in degraded performance and accelerated hardware failure.