Hello, I'm planning on purchasing the Sennheiser HD 515 Headphones, but I am still a bit unsure about a few things. 1) Is a 3.5mm jack the same type of jack that is used with average headphones? 2) Is it possible to use a 3.5mm to USB 2.0 converter with these headphones? (it looks like these headphones only have one jack, but most of the converters I've looked at are made to accommodate two jacks; I suppose for left and right audio) If it is possible to use a converter for these headphones, where can I find one? 3) I am planning on purchasing a mouse from a website called Tiger Direct. I've noticed the prices are shockingly low at this website, and it looks great, but does anyone have any experience with this retailer? Thanks!