I had an Dell Axim X5 and bought the gps solution from pocketmap.com. the reason i bought it is becuase i heard good reviews (saying it was comparable to more expensive solutions like magellan and tom tom) and it was only around $140 for the kit which includes a good CF receiver and antenna extension and software (albeit a little old) of the entire US. I'd recommend it if you're looking to save some money for a pretty good gps solution for your handheld.
PocketMap Navigator