Someone suggested ripping with Windows Media Player? But does WMP encode in MP3 or AAC? I believe MS declined to pay the license for MP3 with Windows XP back in the day.

iPhone plays MP3 and AAC but not WMA.

If you rip with iTunes, check the settings in iTunes Preferences to set the bit rate and the codec you want.

iTunes doesn't crash for me. But Lion seems to be more memory hungry so consider upgrading to 8 GB or more but don't get the RAM upgrade through Apple, unless you get a MacBook Air, which can't be upgraded because the RAM is soldered on.

MacBook Pro RAM upgrades will be tricky but there are videos out there.

iMac, the 27-inch ones are unwieldy but the the RAM slots are pretty easy to access. BTW, the 27-inch IPS screen is very nice, if you bought a display of that size and quality, it's around $1000.

(Also, if you choose an iMac, you have the choice of wired or wireless keyboards (main advantage of wired is it has a numeric keypad) and either wireless Magic Mouse or wireless Trackpad. Consider the trackpad if you like the multitouch gestures on the iPhone/iPad, a lot of them have been integrated in OS X Lion)