i use the globalsat bu353. you can find them on ebay pretty cheap, thats where i got mine (just search for bu353) and i run iGuidance 4 for the streets, and delorme topo for offroad (though ive only tested this briefly)
ive run that gps receiver for years, very very good, and in my opinion much better than delorme's offerings. just fyi though, it HATES being plugged into a hub.