I use Revalver MKIII with Reaper and ASIO4ALL. It only records the guitar, nothing else.
To expand on what ASIO really is; it stands for Audio Stream Input/Output, and it's pretty much a driver that bypasses the audio stream from all the layers that it would go through by conventional normal sound card means, i.e going through windows and through all the programs.
ASIO takes the signal directly through all this mishmash of piss, and straight from the source, to the soundcard, not only DRASTICALLY improving latency, but also retaining quality in uncompressed sound files, such as raw .wav.
Most higher end studio soundcards, amateur and professional, come with asio technology inbuilt, and i recommend that those of you who have this, use it.
For those who don't get that option in ReValver MKIII, you have the option of this:
ASIO4ALL a free universal ASIO driver for Windows that brings ASIO support to users of virtually all consumer-grade soundcards and integrated audio chipsets. It also supports semi-pro and pro digital audio systems.
as taken from Wikipedia, read more about the technology there.
With this software, you should be able to play real time without any delay, with ReValver MKIII, for practice and recording if you want.
I hope this helps some of you, and answers some questions.