I think you need to do a little more research on this. I agree with Merlin. The new chip sets are far more sensitive and will pick up signals where a receiver with an older technology will not.
I don't have a version III but do have a version II sirf Pocket PC by Mio. It was cheap
at under $200 with a color display and could use the Fugawai software
I already had. I do like it so don't get me wrong about what I have to say about sirf.
The big deal is the Time to First Fix being faster. It's done at the expense of accuracy. If you leave it off for more than a few days it loses all the ephemeris data that is used by all GPS's to establish a position so in that way it does not really do anything brand new. It just guesses faster. Perhaps a minor illusion at best. I actually find of my three on board GPS's it reads velocity and altitude the poorest. Those are the hardest readings to compute. With position on the water just how could you know? It does seem to give a result inside the house but only after you fire it up outside. It is basically guessing. My old Garmin
128 with the external antenna gives better accuracy but takes about 30 seconds to start up It has less non volatile RAM so it starts from the ground up most of the time unless you leave it on all the time (you could). My Raychart 400 does about the same as Pocket PC with the sirf chip but has a brighter display and uses vector Navonics chips. It clearly is the best looking albeit small display. The Garmin
128 as a display is basically a joke as it only displays way points and tracks but no chart.
In all the sirf reviews
they say "enhanced sensitivity" but the reality is that it isn't more sensitive. They are just reprinting the manufacturers hype verbatim. It can continue to display a indoors value but not accurately. A GPS signal coming in low over the horizon is distorted and can not be "enhanced" with any sensitivity because it has lost
it's timing through attenuation. It's the time encoded that is what determines the position and you can't make that out of nothing. The fact that is is a poorer signal means it actually took longer to get to you than the receiver can know. It gives the illusion that it is farther away from you than it really is and that assumes you decode the signal totally accurate.
What is most interesting is the new in vehicle navigation
systems are what is driving the market so all the hype is geared towards the problems of "GPS in urban canyons". It's been the big topic for 20 years. They now have added what auto pilots aboard ship have always had - heading and acceleration sensors. They have done it because there is a limit to what you can do with a GPS signal. There is no such thing as "enhanced sensitivity". It's all marketing