I wish to purchase an oscilloscope to help me diagnose and repair analog and digital effects pedals, and to work on and optimize microphones. I'd probably use it on amps and electric guitars too. I need to know what features I need on an oscilloscope to do the work stated above. I have been looking at oscilloscopes on eBay that were $200 or less and there are dozens of them. Mostly used, some smaller ones that are new. If I buy a used one I will make sure that is calibrated and warranteed. There is also one for the PC called Multi-Instrument 3.0 that looks interesting. Here is a link for it http://www.virtins.com/page2.html. If you scroll down the page there is a chart that shows you what the various versions do. There is a Lite version for $49, a Standard version for $99, and a Pro for $199. If I decide to go that route, which one would be best for me? Thank you!