IMHO, an
Itelite ITS-DBS02.2.... and ABSOLUTELY! There are a number of cheap antenna add-ons out there that are very hit and miss. Some will swear they get better range while just as many using the same product will swear their range actually decreased. I say.. if you want a range extender that is proven to significantly extend your range... every single time... you get what you pay for.
I tried the windsurfer and another similar product with no noticeable change in range or performance. Even though they didn't cost much they were a complete waste of money.