Daveyf I'm not sure what you mean by your peamp having a pretty large voltage output. It shouldn't be anything a soundcard couldn't handle. An easier solution would be to get a portable firewire/usb powered audio interface that includes phono ins like the Presonus Inspire. Guitar Center will sell you one for $150 or so. It also comes with a "lite" version of Cubase which is a popular audio/midi sequencer and editor.
How do you download your LP's to your computer?
I would really like to be able to play my Lp's through my desktop, how are you doing that? Does the Desktop need a built in DAC? What program(s) are needed and what other hardware?