Sorry to hear you're having problems. Call a Genius at your local Apple Store and have the pros diagnose and fix your issues. That's what they're there for.
The mail program in Mac has always worked without a glitch for us. Once you get your Mac running to apple specs, you shouldn't need a separate email program unless you're a professional email marketer-then try MailChimp.
I love iPhoto, but there's a version of Photoshop for macs too. Depends how how intense you need to get in your editing. But give iPhoto a try before spending a lot of money.
iTunes-no help from me-I barely listen to music.
Good luck with your iMac. I love mine. We've been Mac people since the late 90's and will never go back to the blue screen of death!