Matt's suggestion is good advice for each gain stage in an audio chain. It gives you maximum punch and less noise from each input.

Note that you may get 60 Hz hum when coming straight out of the headphone jack on your laptop. You can buy a ground loop isolator for $20 to $30 which will safely eliminate this noise entirely. (There is another, cheaper way which carries some risk, so I won't detail it here.)

"My primary musical instrument is the personal computer."