Go to the GPS/Hardware section of this forum, and visit
www.gpspassion.com for reviews.
Personally, I like the simplicity of iGuidance and use that with the Globalsat BT-338 on my x51v without any problems. You can find discounted bundles at semsons.com or buygpsnow.com (find discount codes on this forum under Shopping/Discounts).
Dell's GPS program is basically the same as iGuidance, but I've read that Dell tends to update theirs slower - and iGuidance has free and discounted upgrade paths depending on when you bought the software. Plus, iGuidance comes with a laptop version for the same price (don't think Dell does, but I'm not sure).