1/4 " .. that's just about 8 mm, you'll need a different type of wheel spacer than the one you posted... that one'll increase you stance by about 1.5 - 2.5" by the looks of it!
you'll need this type of spacer...
http://cgi.ebay.com/ebaymotors...photo
careful though, using spacers will increase stress load on your wheel bolts... over time, may not be the best idea.. this is why its better to get rims with an offset matching the stance you want. BUt I know, sometimes, its hella hard to estimate that... good luck!
Ask generic, he has spacers on his ride!!