Thanks guys for the comments.
Drunkbrother: The detectors (4000,4500 & the 5000) do have factory pre set settings so that you can just switch on & go. The 4500 has the options that you can progam 6 different lots of settings for different detecting situations & conditions. For example, if you are detecting exposed bed rock that has low mineralisation or black sands present you work out all the setting that will give you the best result & you can save those. If you are detecting in deeper type ground that has a bit of or a lot of iron sand or iron stone rocks then you can select what settings give you the best result in those conditions & you can save those. If EMI is an issue or you need to use a DD coil & not a mono coil then you can set those settings & save those. ETC ETC. You can do this 6 times which gives you the advantage that if you go from detecting exposed bed rock to say deep highly mineralised ground you dont need to reset your settings each time but just flick a switch & your pre saved setting for the conditions you are detecting in will be there straight away.
Our ground in NZ is pretty quiet & not heavily mineralised like it is is Aussie....especially in WA. The learning curve of these detectors is getting to know how & where to adjust ALL, & there are many, settings from the factory pre set settings to get the very best sensitivity, depth & stable threshold for all the different detecting conditions that you will encounter out there.
Gavin: The 4500 appears & lot more sensitive & better depth. The depth I am getting with the 11" mono, especially on small gold compared to the 3000 has suprised me. I havnt even tried the little joey mono yet & may not even have to. With the 4500 the adjustments you can make with the gain, stabilizer, the manual tune, the soil timing settings, motion & ground balance speeds, means you can really fine tune the detector to the coil you are using. With the GP series you changed coil size to get sensitivity/depth or a comination of both for shallow small gold &/or deep bigger gold. It was always about compromise so hence a large range of coil sizes with the gp models. May be not so much so with the GPX's. Cheers.
Good luck out there.
JW :)