I'm looking to just do some simple recording and looking for a decent quality set up. I plan to use Reaper for recording. If I got something like this: http://pro-audio.musiciansfriend.com/product/Alesis-iO2-Express-Audio-Interface?sku=485880 Could I just do a line in from my amp to that until I can get a decent mic and hear whats recording through my computer speakers? Basically, does Reaper have something like Audacity's software play through option and would using this reduce lag enough to use it?
Yes. With that interface (and your computer is up to par), you can click the ''Record Monitoring'' button in REAPER.

Guitar > Amp > interface > Reaper.

Once you have the REAPER settings configured, arm the track you wish to record on, and click that little button on the mixer FOR that track. youl see a MASTER mixer, and a mixer for that track to the right of it. I believe its the third button from the bottom, to the right of that tracks slider.

I do this, and I dont have any latency issues. : )