|There are a lot of reasons that may cause the mac slow, besides hardware upgrading, there are a few things you can check:|
* Check your Login Items under System Preferences > Accounts to see what you have automatically launching.
* Also check /Library/LaunchAgents/ and /Users/yourusername/Library/LaunchAgents/ for items launching at startup
* Look at what widgets you may have running.
* Launch Activity Monitor and change "My Processes" at the top to "All Processes". Then look to see what may be consuming system resources.
* Take a look at the System Memory tab at the bottom of Activity Monitor to see if you have excessive "page outs", a sign that you may benefit from more RAM.
* Make sure you're not running any 3rd party antivirus app, as many of those will drain resources, reducing performance. They're not needed to protect your Mac.
Also let this Mac clean up tool http://www.anysoftwaretools.com/spe... to perform a health check of the machine. Regards.